I'm going down on the Friday with a work mate. I agree the entrance fee is too expensive. I mainly go to have a look round the gun dealers stands as I don't have a decent gun shop nearby.
I think the oil you want is "Warthog Purdeys Alkanet Root Oil". I bought a bottle years ago and still have it as you only need a tiny amount. Haven't seen it in any shops for a long while now...