Alright Gary,
First off this rule for acu licence has not come into action yet, but will probably be around for the start of next seasons trackdays.
The cost varies from about £80 to £130. The best organisers are www.100pc.co.uk.
If you've never done a trackday before, choose the novice group. Its totally differant to riding on the road. Cadwell has a lot and i mean a LOT of crashes a week so your best off starting steady. Hope this helps mate.