I've heard Edinburgh is a really nice city, I'd love to go there one day!

Here's a link to Oxford Tube, which is another express bus.
http://www.oxfordtube.com/on_and_off_london.php

http://www.dooyoo.co.uk/transport-national/oxford-tube

We used to take Oxford Express though, X90.
http://www.oxfordbus.co.uk/espress1.shtml

Fares: http://www.oxfordbus.co.uk/espress3.shtml