Scampton doesn't have a Stn Ops in the conventional sense - RAFAT is self-supporting in this respect. ATC is your best bet, and I see fabs has already given you a pointer.
As for timing, it's nearly that time of year when RAFAT go on their pre-season trg deployment, but I am not sure what the gen is regarding availability of facilities when they are away - you might find it actually makes the whole thing more expensive, especially if SerCo has to provide cover just for you.
The 'Museum' is only open by appointment - again ATC should be able to point you in the right direction.
STH