A while back I did some digging on this very topic as this was something I contemplated. Whilst there a quite a few jet warbird groups in the UK there are very few who offer flights for paying punters.
I seem to recall a Jet Provost group at Gamston was offering 30 mins. flights for £500, which is a bit rich for my taste
.If you are very flush you could consider doing a type conversion course, which I think Jet Heritage at Bournemouth might offer, but we are definitely talking megabucks here.
As ever, there's always the US, there's usually an ad for The JetWarbird Training Centre in the back of Pilot.