I highly recommend Robin or Raj at Panshangar airfield - call 01707 391 791.
45 minutes from central London, so should be less than that from North London. They have a very tidy Supercub. Robin in particular has something in excess of 1100 tailwheel hours. They allow very tight "bad-weather" (even in good weather...) circuits there too - 500 ft (with a climbing turn to downwind), so you get plenty of landings in each hour. Its about £100 per hour brakes off-brakes on. Enjoy.
BTW, only disadvantage is that Robin flys Weds and Sun only....Raj is also part time.