Oxford is only 55 miles west of Central London and the two cities are connected through frequent bus and train services. A 1 hour 20 min train from London Paddington or a 1 hour 50 min coach via M40 and A40 will both get you to Oxford Station which is close to the city's centre. Make sure not to get off at Oxford Thornhill Park (unless you mean to), as this station is on the outskirts of the main city area.