Not sure if I saw this answered, but are there Oyster-like travelcards for all of Britain? We only plan on spending one day in London and the other days visiting differant areas of Britain-Cardiff, etc. Thank you
No.
Maybe you are thinking of the BritRail pass. You purchase it for a specific period of time, eg 3 days, and you can do unlimited travel by train during that time. With the flex pass option you can purchase x number of days of travel to be used over a period time such as two months; this is great if you are doing stop and go travel through the UK. www.BritRail.com
There are Oyster-like cards operating in other parts of the UK apart from London, eg the Walrus card in Merseyside and the Pop card in Tyne and Wear, as well as on some train routes. However, it is a a long way from becoming nationwide, although government policy is for it to become so at some time. Practically this isn't going to be for some years. As each rail franchise comes up, smart ticketing is part of it.