BEWARE - Waitrose Thame has subbed out their car park to Britannia Parking. If you go over the 2 hour limit you will get a mugging with a bill for £40 (£70 if not paid immediately). Their signage is almost invisible (I have marked it with a yellow arrow) and when I complained they said 'tough shit, it is our policy'. Bandits.
My new policy is never to buy from Waitrose or John Lewis again.