You will need the following:
ARC-1 flight computer & manual (Whizz wheel)
CAA Southern England 1:500 000 chart (for the nav exam)
5" navigation protractor
16" navigation scale rule
chinagraph marker
PPL Logbook
PPL textbook series (AFE or Trevor Thoms)
Don't bother with an electronic flight computer as you will not be allowed to use it, especially in the exams. You might need a CAA Northern England 1:500 000 chart if you are training in the north although the southern chart is required for the exam.
It might be nice to get yourself a knee board and a bag to carry everything in as well. One peice of advice on knee boards, if you are training in a PA28 then dont bother as they snagg up on the yoke