The first thing you have to remember is that Oxford University is made up of various colleges in various locations within the city. So there is no campus as such and it’s a VERY good idea not to use the word campus in Oxford. Each college has it’s own grounds. Some, like All Souls, are permanently closed to the public. Some will allow people to walk through their grounds. There is no way of knowing which colleges are open to the public on any given day. The best way to visit is to enter a college and walk into the porters lodge or talk to one of the bulldogs or scouts on the gate. These people can easily be spotted, they all wear bowler hats ( DON’T call it a Derby ). They will advise you if you can walk through the grounds, if you can’t enter they may tell you which colleges are open. They are very important people and you do have to ask very politely ( they terrified me when I was a student - and my father was a staff sergeant in the Sherwood Foresters Regiment ).
Another good source of information about Oxford colleges is to be found in three Oxford pubs: The Eagle and Child ( called the Bird and Baby ), The Lamb and Flag ( the Slag ) and The Turf. The Bird and Baby and the Slag are both owned by St. John’s college and employ students behind the bar, so does the Turf. Buy them a drink and ask a member of the bar staff.
Do take one of the walking tours from in front of St Mary the Virgin’s on The High ( High Street ) or outside Trinity College on The Broad ( Broad Street ) - the guides can often tell you which colleges are ’open’.
Banbury Road in Oxford is full of reasonably priced B&Bs. I’m sorry I can’t recommend any particular one, I either stay with friends or put up at the Cotswold Lodge ( very pricey I’m afraid ) when I’m in town.
One place that you should consider is the Lintern Lodge on Lintern Road. It’s a ’Best Western’ and reasonably priced and in a great location. Book early if you want to stay at the Lintern.