My wife and I will be in London from a Monday night (late flight) until catching a train out to Bath Saturday morning. So 4 full days. Which Osyter card or travel pass would be best for us? If it is likely more cost effective, I would like to take advantage of some of the travel card 2-4-1 offers. Thanks!
The 2for1 offers are sponsored by National Rail. To take advantage of them, you need to buy paper travelcards with the National Rail logo on them at a National Rail station. The travelcard you can load on an Oyster card won't work for those offers. See the offers and print vouchers for the ones that interest you here.
If you will arrive at Heathrow and the only ride you will take Monday night is from LHR to your hotel on the Tube, then just buy single tickets for that ride. In the morning go to the nearest National Rail station and buy seven day, zone 1-2 paper travelcards. Even though you'll only be using them for five days (Tuesday-Saturday morning), they will be cheaper than five one day travelcards.
If you will arrive at Gatwick, buy your seven day, zone 1-2 paper travelcards at the Gatwick train station. Take a Southern train to Victoria and the Tube from there to your hotel. Buy regular train tickets to get from Gatwick to the border of zone 2. Your travelcards will cover you from there to Victoria and from Victoria to your hotel.