There's fook all in Cambridge apart from a big river & me!
Don't know of any shops selling vinyl except a few 12"'s in HMV
Andy's and the one just up from it, Max's, Parrott and that one opposite, all closed about 3 years ago or more.
There's never owt on the market and I'm sure Andy's stall on Ely's Saturday market has long gone (could be wrong, got a phobia of Cathederals / cities)
However, there's a few decent pubs and lots of top totty about when the sun's out so check the long term weather forcast for those dates.