We plan to fly into Heathrow from Canada early on a Friday morning in July and wish to travel from there to Oxford. We should arrive in Heathrow by 6:45. Past experience tells me that it's difficult to predict the time it will take to get through customs at Heathrow; last time it took 1.5 h. I am, therefore, uncertain whether to book a taxi to Oxford in advance or to take the Heathrow Express to Paddington, then the train from Paddington directly to Oxford. The advantages of taking a taxi would be no transfers and lugging of suitcases. However, our time in customs would be difficult to predict and, at that hour, we could get caught in nasty commuter traffic. This might make the train option faster. If we do take the train, do we need to book in advance for the Heathrow Express? If catching a train spur of the moment isn't difficult in the morning, this might be ideal. I know that there are four trains leaving Heathrow for London each hour. Similarly, if we can buy 'anytime' tickets from Paddington to Oxford and not run the risk of advance sell-outs, it would give us added flexibility. I don't know whether we will be flying into Terminal 5. We are favouring British Airways but may decide on Air Canada. Money is not the main consideration in making my decision; I know that the Heathrow Express isn't cheap.