Visiting Oxford

I'm going to be in Oxfordshire with a bit of free time on Saturday afternoon, and as I've only been to Oxford once and didn't get to see much of it then, I'd like to pop in for a while if I can. I'm planning to park at one of the Park and Rides, wander around for a couple of hours (rather than going to see anything specific, as time is limited and I'll be with people who don't really do museums and such), then head off for my evening engagement. Does anyone have any recommendations for a)places to wander to/around and b)places to have coffee and cake?

Bleagh

Having been fairly pleased that I'd managed to remain reasonably productive in the last few days (in work and housework terms, anyway) despite this season's obligatory stinking cold, I appear to have hit a wall somewhere. Grand total of not a lot done since about yesterday lunchtime - energy and motivation distinctly lacking, stuffed nose and chesty cough still distinctly present. Hmph.