There's quite a lot going on in the Oxford area. The folk club runs on fridays from about 8.30 weekly (get there earlier on guest nights)Click here for details
There's plenty of sessions in the area too - in Oxford itself there's the big one in The Half Moon, St Clements every sunday (mainly irish but depends who's there, can be quite english). A new one has sprung up at the Chester Arms off Iffley Rd (every 2nd Tuesday - French dance music). The others I know are in Wallingford and Steventon but I can't remember where. If I find the details I'll post them here.