I'd have thought that it would depend on where you're staying. I don't think you'd be allowed to access the library at my college, for instance (unless someone specifically let you in).
I rang the admissions office today for St Hugh's and they told me invites should be coming out over the next week or so
Thanx. At least I don't need to check my email so frequently this week... But I need to get a convenient visa service next week. That is how Oxford tormenting students