Is it possible to drive down to a tube station West side of London (off M4 / A4) and be able to catch tube in (St.Pauls area)? Want to leave the car over night - would it be safe / how much? Looking to take a family of 6 to London and finding cheapest way - trains still seem very expensive but maybe worth the hassle factor??? Travelling from Swindon - sometime mid August - no fixed dates yet.