I tried to buy a same-day return ticket for 70 pounds (about $100) from the UK web site. It would not allow the transaction to complete, because I entered my US address (in required fields). Tickets purchased 7 days or more in advance get mailed, and the address must be in the UK.

So, I'll wait until I get within 7 days of my trip and buy the ticket then. In that case, it will be held at the will-call window at Waterloo Station. It looks like that will work, if availability remains. Isn't FlyerTalk terrific?

Any other ideas?

Bruce