Cheeky,

Just one point I'd like to ask, will you be traveling to/from all 6 zones once you get to your destination? Also what time will you be arriving as the cheaper travel cards aren't available until 9.30am Monday to Friday.

If you only plan to hop about central London, then why not just queue at the ticket counter and ask for a zone 1 and 2 travlecard and an extension from zone 6 into zones 1 and 2. You can still pay for it with a Visa card and save money, although perhaps it will cost you 5 to 10 minutes in the queue depending on what time of day you arrive.

Also, if you are going to be very central and just use the buses, an all day, all zones bus only pass costs just £2

Just some thoughts! @:-)