It takes between two to three hours to get to Oxford from London. Of course, much depends on your choice of transport. If you are on a shoe-string budget, pick the bus as your preferred mode. There are bus services that take you to Oxford for only a pound if you book early enough, but the service, understandably, is not that great. There are other bus services, of course, and the buses are extremely regular. If you are a student, be sure to produce your ID because it will get you a hefty discount. A more accommodating budget might allow you to take the train, which will get you there faster and have more comfortable seats, but I'll recommend the bus. It allows you to take in the journey and the world outside the window. Where you stay also depends on your budget, and you will have plenty of options. And if you can find a friend of a friend of a friend who lives there, try and convince them to put you up for a couple of days. Otherwise, there is always a good old B&B.