Possible honey fungus problem?

Over the last few years the trees in our old orchard have slowly died and we believe it is because of honey fungus. Recently we dug down to the roots of the plum tree that dies last year and there was white underneath the sheath of the root bark. We have had a sort of honey fungus appear in the Autumn so put it down to that. The only thing is though is that we didn't see or could find any of the telltale black bootlaces associated with honey fungus. Are there different types? We also have a Warickshire drooper near by which has been looking worse for wear and I dug down yesterday and to my dismay when I hit a root I found the following:





Below is a picture of the Victoria plum that dies last year in the foreground. We left it like this to possibly put a climbing rose up it but unfortunately as we were digging a hole for it is when we found the roots had a similar look the the pictures above.



We also have a quince tree near by off to the right which is also this year starting to look a bit worse for ware and we are concerned it may be going the same way. What can we do?! It's getting to the point where we might not be able to have any fruit trees at all in the garden which is quite upsetting. From what I have read so far it sounds like we would need to do some serious ground work with a digger and digg everything thats infected out but that sounds like a seriously big job and not necessarily full proof. Any advice would be greatly welcomed! Thanks