I would like to purchase an Oyster Card before I leave for London but there's an $18 shipping fee if I go through the BritRail website. Does anyone know a cheaper route?
I bought mine right at the box office at Heathrow airport. It's totally easy, hassle free and you don't have to pay and handling fees. There really is no reason to get it shipped to you prior to your trip.
There is no advantage to buying an Oyster card in advance. If you're flying into Heathrow, buy it there.
I completely agree with the others. Buy the Oyster Card at the first station you visit in the U.K. There's a £3 deposit, which I believe can be refunded when you leave the country. I didn't bother, I'll just use it next time.
Happy travels!
If you plan to buy a 7-day pass and are arriving at Heathrow, ask whether you'll save money buy buying just the zone 1 pass and paying the supplement for your trips from/to the airport and any other side trips (e.g. Kew Gardens). If arriving at Gatwick, tube from the airport isn't an option. I spent a week in London last year and never got out of zone 1 (except for Windsor, which required an inexpensive train ticket from Paddington station).