In reply to BusyLizzie:
Don't have any particular recommendations I'm afraid (though I've known people stay at the travelodge... a bit noisy but not bad). If you want a slightly different experience, try the Victoria Inn, but may be booked out by now (and a bit more expensive).
Main thing is to book something quickly, though - Durham isn't that big a place and accommodation is going to be pretty busy that weekend with lots of people doing the same as you...