We're flying into Terminal 4 at Heathrow this September, and we have free passes on the Heathrow Express into London thanks to our London Plus Pass. But they moved out of Terminal 4 so we have to catch the tube or train to the Terminals 1, 2 and 3 stop in order to board the Heathrow Express to Paddington. Then at Paddington we'll jump on the district line for a 10 minute ride down to Earls Court. Sound crazy? Yes, we could just sit down on the tube directly into Earls Court, but it would take nearly an hour with 20+ stops on the way. I like fast trains and a "free" ride on the HE sounds too good to pass up.
My question is, we have to buy Oyster Cards at some point at the airport or at Paddington. We'll need them for the tube ride to Earls Court from Paddington, and at various times while in London.
Having never been to Heathrow, where is the best location to buy them? I assume it's easier at Heathrow than at Paddington. Is there a desk at Terminal 4?
Thanks for your help!