I tagged along on a Castle Combe track day (on my Guzzi Griso!) with some of the WB crew a couple of years ago, super friendly and Gerry is just about the most helpful guy you can wish for. My tyres were okay to ride there and back on (just as well as getting the lump in and out of a van is not easy) but I wasn't exactly tearing up the circuit, did manage to get past a 'less experienced' R1 rider though and had great fun exploring mine (and the sidestand's) limits.
Definitely recommended