Pretty sure Church Fenton or Linton-on-Ouse accept guests to their respective ATC units. Spent a week on Fenton Zone myself a couple of years ago.....they really do hate civilians....after a week of doing FIS to PPL students I'd really had enough too.
Still, i'd suggest an RAF ATC unit is worth a visit, quite interesting watching the military ops and if you can sit in with the bloke doing MATZ transits or watching zone, you'll get a load of VFR stuff too.
RC