Closest airfields for you would probably be Denham (up the A40) or Elstree (up the M1). You'd be able to get to either in less than an hour. Biggin has lots of choice of schools, but it's quite a slog through the suburbs.. .. .Cabair have got schools at Denham, Elstree and Biggin. Many consider them a bit pricey to learn at, but for a trial lesson they may be a good choice - smart and reassuring for those nervous first-timers. Another good alternative may be the British Airways Flying Club at Wycombe Air Park - never flown with them myself, but they have a good reputation. Lots of other, less starchy just as good schools around, but many people taking first GA flights are used only to the airline experience and can find the more down-to-earth clubs a little disconcerting initially.. .. .As far as I know, trial lessons everywhere are much shorter than 4-6 hours - more like 15 mins briefing, half an hour's flight then a 15 minute "any questions" session. No doubt you could arrange something longer if that's what's needed.