Transportation
London
In London, you need to buy an oyster card initially to travel in train/bus/tram/tube. It will cost you £5 for the card and you may top up with the needed amount to use for your travel. For monthly pass or weekly pass based on your travel, you may check in www.tfl.co.uk site or inquire at the station counter.
Other Cities
Check with location specific sites or national rail site or check with friends & relatives who is staying in that location.www.tfl.co.uk site or inquire at the station counter.
Taxi
Minimum £8 in London and will be cheaper outside London. But, public transport is good in London and a taxi is not needed.