Hi Grab, the tunes you need to learn are those which are played around the sessions in Cambridge. Every session has its own favourite tunes although there are a few old standards which everyone plays. We, at the Jug play one set while The Sloop, Barton on Humber, where Skipjack plays have another set and the Maltings at York yet another set. There is some overlap and musicians who travel to other sessions generally carry tunes from one session to another. It might be an idea to ask at your local session if you could use a tape recorder and then listen to the recording till the tune is in your head. There are many sites for midi mucic and one I would recomend is Barry Tailor's who has tunes from Scotland, England, Ireland, Canada, USA, and Wales.
Cheers Bill