If you are going to the Secret Garden Party check out some of the surrounding countryside. Godmanchester is a lovely village very close to Huntingdon. Stroll pass canal boats, check out the Fenland countryside or visit a nice village pub. A bit further afield St Ives has a great old bridge and river front with a nice tea room vibe.
Also - someone has to mention it - Pear Cider at Glastonbury!