Living in Kent, there are obviously two NATS locations providing ADV/ADI within normal commuting distance ie Gatwck and London City. That said, at Farnborough we had no less than two ATC staff who commuted daily from Corsham (Wilts), several from the Bournemouth area and one from Swindon, plus one of the airfield fire service personnel commuted from - Kent! So it's really up to you for these distances. If you do get through the training of course, there are other NATS units much further away such as Manchester and Glasogow from where you would probably prefer not to commute. From what I've read in these pages, you don't get much choice as to final posting and what discipline you're trained in so you may not even get 'streamed' for ADC training.