We use streetcar. £6/hr, plenty of cars near us (North London) and easy to book. Very useful for short trips or longer days out. We also used it for a week away once, but in retrospect a standard hire car would probably work out cheaper for long journeys. You get 30 miles free petrol per day, then there's a per-mile charge (I forget how much - pence). To top up the tank you have a card to pay for petrol, and if you use it to pay for a carwash, you get money back (for your time I guess), which equates to a free hour's driving.