James heartily recommends Simon Warren's book 100 Greatest Cycling Climbs: A Road Cyclist's Guide to Britain's Hills, which features Dunkery Beacon and Porlock Hill (a 25% gradient!). If you're into cycling and can bring your own bike (and a lock) IBD is a great opportunity to ride some of these climbs. Otherwise you can hire bikes from Butlins rental shop will be open on the afternoon of the 6th from 2pm - 5pm.
They also have available items such as towels, irons, mobility units etc to rent in case anyone needs anything. From here you can rent a mountain bike for 4 days for £25. If you wish to rent it for a half day on Wednesday or Thursday they can do so for £8. If you wish to do that let ATP staff know by Tuesday night.