Thank you everyone, I am going to water again in the morning and also feed them tomorrow. I must admit, my compost is rubbish, it doesn't seem to be holding any moisture for any of my plants.....lesson learnt, next year I will have my own compost or buy better quality and not using growbags either....cheap black buckets from Morrison's is the way to go, all my plants in black buckets are thriving
Ok, having read up on BER and blight - both early and late (I didn't realise there were two types) I am still undecided, mainly because I do have discoloured leaves but not discoloured stalks and I need to inspect the leave more closely in the morning.
So, although I hope that it is BER I'm not taking any chances and tomorrow will take preventative measures for blight. I am going to remove more leaves from the bottom and any discoloured leaves. Unfortunately I can't move the plant as I have nowhere to move it to unless I move the whole GH around and that may mean damaging plants.
I will do my best to not lose my plant and will update you later in the season....or sooner if it dies Thanks everyone for your help, lots of support as always
Orchid Lady, it's not BER. BER produces a dark leathery patch on the fruit.
Looking at the second photo in your 20.34 post, you've got a sick plant. Signs of several fungal problems and probably nutrient deficiencies too. I'd pot it up into a bigger pot with good quality potting mix and isolate it from the healthy plants. I'd also lay off the watering.
I never water my tomatoes until the leaves begin to flag - I then fill the pots to the top with water (I allow a 6-8" gap between compost surface and pot rim). I do this consistently - last summer I was only watering my tomatoes once or twice a week at the most - out of 27 plants and a huge crop of tomatoes I had only one fruit with BER.
Tomatoes do not need constantly moist soil, it impedes the take up of calcium which causes BER. I only fertilise my outdoor tomatoes twice - once when the first fruits have set, and again when the second truss has set. This helps prevent imbalances in the compost which can also contribute to BER.
I wrote this yonks ago, just in case anyone may wish to give it a glance.
"Blossom end rot occurs when there are insufficient calcium levels in developing fruit. This is most common when the first trusses are forming and calcium demand is high.
As water transports calcium around the tomato plant the condition is usually linked to inadequate or irregular watering.
Tomatoes need the equivalent of 2-4cms rainfall every week, though the amount of water given is less important than maintaining consistent water levels. Watering daily, at least, will be necessary in hot conditions.
As little as half-an-hour of water deficiency can cause the condition to develop. Pick off and compost any fruits that have been affected.
Mulching around tomato plants with grass clippings, straw or hay will prevent plants drying out."
Wow, thanks everyone for all your replies, even if they have left me a bit baffled!! It seems that it could be a number if things. I had said on the Forkers thread just now that I was going to water little and often, but I'm not going to do that.
Here is my plan of action that I have decided based on the various inputs:
I am going to repot the plant into a black bucket and move it the nearer the door of the GH away from other plants.
I'm going to remove the bottom damaged leaves.
I will feed with Epsom salts
Then continue to water to keep the compost damp only but ensuring it doesn't dry out at any time.
I think that's as much as I can do and if it doesn't work, well lesson learned for next year.
Thanks again everyone......and no falling out please, everyone has their ways that work, as a 'newbie' I am open to suggestions and help and no doubt over the years will find what works for me
Good philosphy OL. You've had a go at so many new things this year and we all live & learn.
I find that with my veggies some things have great years others not so good. It's disappointing when things fail but not the end of the world. I take a more relaxed view these days, if they do well great if not tough luck.
In my GH the Gardener's delight are doing fine, few grotty leaves have been removed, the St.Pierre are pants, they've had the same care, so I just won't grow them again ...That'll teach them ! The outdoor ones grown in buckets, which are an outdoor variety but I don't know what, so are called Dave after chap who gave me the first plant, are doing very well and will ripen before GH ones. If something were to happen to them I'd have a bit of a sulk but would try and think that at least I don't have to water them & I have some seed left fom last year that I can use for next.
I find tomatoes absolutely fascinating plants but there is a problem with an awful lot of contradictory advice about how to deal with various problems as well as the general growing care of the plants. Like Dove I only water my toms when they show signs of needing it, I give a feed when the first fruit have set (if they're in fairly poor soil like at my allotment) but haven't yet fed my greenhouse toms as they were potted up in good compost a few weeks ago and really don't look like they need it. That part though is down to personal choice, last year there was a chap on GW who grew his plants in half a normal sized pot of compost, he fed and watered every day and his fruit looked (and apparently tasted) delicious. I don't have the time, expertise or inclination to do that myself though, so I stick with what's worked for me so far and carry on learning.
I will say that there's a whole lot of extremely knowledgeable people on here who are a godsend when Google is of little use, Italophile in particular really knows his stuff and has kindly offered me his advice in the past. I guess we're all on a quest to enjoy that wonderful flavour of homegrown tomatoes and it's lovely to learn about them and read people's tips along the way.
Thanks Leggi and I agree totally. I had already read the articles that Buddyboy showed me before I came asking for help, articles are great but you can't beat 'speaking' to people who have experience of the problems themselves and have years of knowledge I was actually secretly hoping Italophile would pop up and help me as I'd heard he was a bit of a whizz with tomatoes
Anyway, I have done as I said above with the exception of feeding them Epsom salts as I need to go and get some and have been busy cutting bushes!! Repotting an established tomato plant is easier said than done so I hope I haven't damaged the roots, I was careful
Posts
Thank you everyone, I am going to water again in the morning and also feed them tomorrow. I must admit, my compost is rubbish, it doesn't seem to be holding any moisture for any of my plants.....lesson learnt, next year I will have my own compost or buy better quality and not using growbags either....cheap black buckets from Morrison's is the way to go, all my plants in black buckets are thriving
Ok, having read up on BER and blight - both early and late (I didn't realise there were two types) I am still undecided, mainly because I do have discoloured leaves but not discoloured stalks and I need to inspect the leave more closely in the morning.
So, although I hope that it is BER I'm not taking any chances and tomorrow will take preventative measures for blight. I am going to remove more leaves from the bottom and any discoloured leaves. Unfortunately I can't move the plant as I have nowhere to move it to unless I move the whole GH around and that may mean damaging plants.
I will do my best to not lose my plant and will update you later in the season....or sooner if it dies
Thanks everyone for your help, lots of support as always 
Orchid Lady, it's not BER. BER produces a dark leathery patch on the fruit.
Looking at the second photo in your 20.34 post, you've got a sick plant. Signs of several fungal problems and probably nutrient deficiencies too. I'd pot it up into a bigger pot with good quality potting mix and isolate it from the healthy plants. I'd also lay off the watering.
I never water my tomatoes until the leaves begin to flag - I then fill the pots to the top with water (I allow a 6-8" gap between compost surface and pot rim). I do this consistently - last summer I was only watering my tomatoes once or twice a week at the most - out of 27 plants and a huge crop of tomatoes I had only one fruit with BER.
Tomatoes do not need constantly moist soil, it impedes the take up of calcium which causes BER. I only fertilise my outdoor tomatoes twice - once when the first fruits have set, and again when the second truss has set. This helps prevent imbalances in the compost which can also contribute to BER.
Italophile is the expert and can explain the theory better than I can, but this article is helpful - you'll see it advises reducing watering to prevent BER http://extension.usu.edu/files/publications/factsheet/pub__8956068.htm
However, I agree with Italophile - the OP's tomato does not have BER
Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.
I wrote this yonks ago, just in case anyone may wish to give it a glance.
"Blossom end rot occurs when there are insufficient calcium levels in developing fruit. This is most common when the first trusses are forming and calcium demand is high.
As water transports calcium around the tomato plant the condition is usually linked to inadequate or irregular watering.
Tomatoes need the equivalent of 2-4cms rainfall every week, though the amount of water given is less important than maintaining consistent water levels. Watering daily, at least, will be necessary in hot conditions.
As little as half-an-hour of water deficiency can cause the condition to develop. Pick off and compost any fruits that have been affected.
Mulching around tomato plants with grass clippings, straw or hay will prevent plants drying out."
Wow, thanks everyone for all your replies, even if they have left me a bit baffled!! It seems that it could be a number if things. I had said on the Forkers thread just now that I was going to water little and often, but I'm not going to do that.
Here is my plan of action that I have decided based on the various inputs:
I think that's as much as I can do and if it doesn't work, well lesson learned for next year.
Thanks again everyone......and no falling out please, everyone has their ways that work, as a 'newbie' I am open to suggestions and help and no doubt over the years will find what works for me
Everyone finds a way that works for them - I find that understanding the science behind the theory really helps.
Good luck
Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.
Good philosphy OL. You've had a go at so many new things this year and we all live & learn.
I find that with my veggies some things have great years others not so good. It's disappointing when things fail but not the end of the world. I take a more relaxed view these days, if they do well great if not tough luck.
In my GH the Gardener's delight are doing fine, few grotty leaves have been removed, the St.Pierre are pants, they've had the same care, so I just won't grow them again ...That'll teach them !
The outdoor ones grown in buckets, which are an outdoor variety but I don't know what, so are called Dave after chap who gave me the first plant, are doing very well and will ripen before GH ones. If something were to happen to them I'd have a bit of a sulk but would try and think that at least I don't have to water them 
& I have some seed left fom last year that I can use for next.
I will say that there's a whole lot of extremely knowledgeable people on here who are a godsend when Google is of little use, Italophile in particular really knows his stuff and has kindly offered me his advice in the past. I guess we're all on a quest to enjoy that wonderful flavour of homegrown tomatoes and it's lovely to learn about them and read people's tips along the way.
Thanks Leggi and I agree totally. I had already read the articles that Buddyboy showed me before I came asking for help, articles are great but you can't beat 'speaking' to people who have experience of the problems themselves and have years of knowledge
I was actually secretly hoping Italophile would pop up and help me as I'd heard he was a bit of a whizz with tomatoes 
Anyway, I have done as I said above with the exception of feeding them Epsom salts as I need to go and get some and have been busy cutting bushes!! Repotting an established tomato plant is easier said than done so I hope I haven't damaged the roots, I was careful