Are these only available online (it says they take 2 weeks to come) or is there any way to buy one on the day? I note they cost £20.
Going to London for 4 days with my 9 treat old and a 17 year old (from abroad so she won't use her Oyster card again) - staying in zone 6 and going into and around zone 1 every day . Is it worthwhile? I just use my debit card nowadays..