I am a Malaysian and my friend is Belgian – both senior citizens. We shall be arriving St Pancras on 19th June and will depart on 23rd June. We shall be staying at Bayswater. During our stay we would like to visit the Bank Museum and other museums; Covent Garden; a London Tour. Appreciate your kind advice on the tube/metro cards for the duration of our stay; where to buy them and the cost. Is there a refund if not utilized fully…?