http://www.knockhill.com/trackdays/index.php?page=1
£45. Which is actually pretty expensive for the tracktime you get to be honest, £55 gets you into one of the open pit day sessions (for comparison, the evenings I've done I think we did 28 fast laps, on the one open session half day I did I put in about 100 laps despite breaks and a crash). If you want top value, really the open pit days are the only option but they mix up the loons with the sane, the track bikes with the commuters... Not ideal. This is more expensive but more controlled.