Thanks for that chaps, some very useful pointers.
I wasn't sure how the "test-drive" worked etiquette-wise, but I guess it's only fair of the group to expect me to want one (at my expense, obviously). From the telephone conversation I've had so far it seems to be a very friendly group, although I don't believe they have a web-based booking system.
Roll on Saturday and we'll see what there is to see.