Speaking of ATZs and places around them, Farnborough North recently offered me an interesting hybrid solution as I was transiting North Weald ATZ under Stansted CTA: keep the Farnborough squawk but contact North Weald, then come back to Farnborough's frequency. When I asked if I'd be better off deviating to the south, halfway between North Weald and Stapleford, Farnborough ATC said there was still plenty of North Weald traffic out there and I ought to let them know anyway.