I'm afraid I don't agree that you will need hundreds of trees in a garden that size. You would be better to research your conditions and choose a few appropriate specimens perhaps with shrubs as well. But the first job is to decide what you want from the garden.
I'd also go with a woodland garden/orchard down that slope. You want to remove as much lawn as possible, as pushing the mowers up and down there would not be fun.
You need extend your patio outside the house, perhaps a pergola for privacy and few small trees to link.
A well designed meandering path down the slope would make your garden feel huge (include a few points to pause of the way down e.g. rope swing, bee hive, water feature, hidden greenhouse, feature stones) but you need a reason to make that journey worth while at the bottom of the garden. Sunken seating area was good call.
£10k should cover the hardscaping if you were to do the work yourself (I did it, with zero experience, the correct tools and plenty of YouTube) but the planting for a garden that size would be eye watering if you were to do it in one go. Which is eye a greenhouse will be invaluable. If you're going to get professionals in for hardscaping, or you want it terraced and more contemporary- your budget could easily triple.
It might be worth spending the money for designer to do some plans (check their portfolio as there's a few frauds) then doing it yourself from there.
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You need extend your patio outside the house, perhaps a pergola for privacy and few small trees to link.
A well designed meandering path down the slope would make your garden feel huge (include a few points to pause of the way down e.g. rope swing, bee hive, water feature, hidden greenhouse, feature stones) but you need a reason to make that journey worth while at the bottom of the garden. Sunken seating area was good call.
£10k should cover the hardscaping if you were to do the work yourself (I did it, with zero experience, the correct tools and plenty of YouTube) but the planting for a garden that size would be eye watering if you were to do it in one go. Which is eye a greenhouse will be invaluable. If you're going to get professionals in for hardscaping, or you want it terraced and more contemporary- your budget could easily triple.
It might be worth spending the money for designer to do some plans (check their portfolio as there's a few frauds) then doing it yourself from there.