Also not in oxfordshire but closer than leek is ESTC near leicester, they offer training days once a month taken by ACU accredited coaches full day is only 20 quid, it's normally split into ability based groups no bigger that 6 riders per group so there is something for everyone.
Dates I think are on the website ESTC.co.uk if not email the club secretary Gail and she'll book you on.
