When visiting my sister-in-law who lives in Oxford, she recommended the airline. It was a great and easy way to get between Heathrow and Oxford.
We purchased our return tickets in advance on line for £29 each, and used a print out of the confirmation email as our ticket. There's no discount for buying the ticket in advance, but it was nice to have it all worked out. For the bus from Heathrow, you can get any one within 24 hours of your reservation. For the bus from Oxford, you have to be within 2 hours, and my SIL says they can be pretty strict about it.
It was a little difficult to find the proper bus bay at Heathrow (#10 at Terminal 5), since that information wasn't included in the email, but that also could have been the jet lag. (Also, we're Americans, not used to needing so much information about public transit...)
We arrived in the middle of the day on a Wednesday, and the bus was slightly late and completely full for the ride back to Oxford. For the return at 5am on a Saturday, the bus wasn't too full when it left from Gloucester Green, but it did end about 1/3 full by the time we'd left all the Oxford stops.
There is free wifi onboard, and the connection is strong and consistent. There are also plugs at every seat. Both our coach drivers were quite friendly. read more