The most up-to-date public transport network maps for the city of Oxford, UK, are produced by Oxford’s integrated bus network provider. Click the image to see a page with the latest pdf maps. On that page find Network Map Downloads. The pdf maps include the Oxford City Centre Map and the Oxford Cityzone Map, which covers the whole city.
On the same page you’ll find links to details of the ‘Airline’ buses that go between Oxford, Heathrow and Gatwick airports and the ‘Oxford Tube’ bus line between Oxford and London.

For longer distance buses in Oxfordshire and beyond, try the national Stagecoach website.