Mike, I have heard quite a few elderly people say, 'Oh we can't be bothered with gardening; we've had the whole thing paved over'. They don't seem to realise that gardening would not only extend their lives, but extend the quality of their lives.
Fencing D, you do not say in the description that we forumatti can access, where you are in the UK (or indeed in the world). This could affect the choice of plants. The lovely old brick wall; is it quite short and is there an alley way beyond it? If so you may feel that for security and privacy you may want to put up some trellis there (not necessarily attached to the wall if it is fragile). Do you know the orientation of the garden? Does it face South?
Do you like a really modern style? That would work best in that space I feel. I suggest that you google small urban gardens and then come back to us for more advice once you have seen ways of dealing with the space that you really like.
Good luck with it, I'm sure it will look fabulous very soon