We will be arriving in Heathrow on a UA flight from the US midweek, mid day. We want to take the bus to Oxford. It looks like we walk to the Central bus station, buy a ticket and take a bus from there. It appears there are 2 bus companies. If so, idoes a make a difference which one to take? Looks simple enough, am I missing anything? Thanks!

We've taken both, and there didn't seem to be much difference between them.

There's only OxfordBus, National Express sell tickets for OxfordBus

The bus is called The Airline ( Oxford Bus Company ) . You can purchase your tickets on the bus. If arriving at Terminal 5 just exit from Arrivals and the bus stops at stand 10. For Terminals 1,2,3, you'll need to go to Central Bus Station stand 15. I believe you can get a bus from Terminal 4 to either T 5 or Centeal Bus Station.

Thanks -- this is very helpful.