We were in London last November and had such a good time, we've decided to return this November. Last year, we visited many of the main destinations, and took advantage of the 2-4-1's, so we purchased the rail tickets with our pre-printed pictures; not an Oyster card. We also used the buses everywhere in the city, using the Tube only once, for travel to London from Heathrow.
This year, we'd like to primarily use the buses again, only using the Tube for travel to and from the airport. We don't need to take advantage of any of the 2-4-1 offers. So, the question is:
Can we use an Oyster card for travel on the buses?
Can we buy a 7-day Oyster card at Heathrow?
If so, how much extra should we put on the cards to travel to and from the airport? (Staying in Soho, near Green Park station.)
Will we need to bring pre-printed passport pics?
Anything else you feel I should know that I've forgotten to ask?
Thanks in advance for the help.