Wood for the trees

First, apologies for absence, been at wooden beach house on Danish east coast (my wife is Danish and needs to return regularly for smoked fish, salt licorice and walks in the forest. I have become a bit obsessed by trees, as need to replace some 'senile' silver birch that are in danger of crushing the beach house roof. Have also been scouring catalogues here for fruit trees for our bank at the back of the plot (see Howard's map below). Looking for an old-school, crisp, maybe Kentish, apple that would do well in London, so if anyone has any suggestions, please let us know?