Ladbrokes you need to check the rootstock the apple is grafted on, this question is otherwise unanswerable. eg if M9 (which I suspect) it needs six to ten feet from other M9 apples, but your peach needs twelve feet of space from another tree.
Prune according to the shape you want. Do the apple now but prune the peach in May when its sap is flowing – all stone fruit trees (plums, apricots etc) risk succumbing to silverleaf if pruned in winter.
All this information is in my first book chapter 18 which I urge you to check over. Also tips on varieties – Braeburn is highly susceptible to scab and makes nice fruit only in dry springs and summers like last year. So although £4 is cheap, the return may be low as well. Sorry but that is how it is. Apple varieties with some resistance to scab and canker include Sunset, Ribston Pippin, Fiesta, Suntan, Topaaz and Kidds Orange, the latter is my favourite for flavour.