Last year I went to Millbrook for a novice track day training session. The instructor was fantastic, I learnt loads and it was brilliant fun. I wasn't racing against anyone else, just learning how to handle my Zed properly. If you want to compete against others it may not be what you want but I can highly recommend Colin and his staff at CAT driving training, based at Millbrook. They do a range off different training packages, not just the one that I chose.
I enjoyed everything that I did but the handling circuit was the best as I was driving in a huge storm, the track was really slippery, I was flying round and I came to realise just what stickability the Zed has, even in poor conditions. It was also good to be able to go at 120mph and above and not be looking out for flashing blue lights in the rear view mirror