If motorway parking was reasonable they would probably get a good income from it, all the ones I've seen have 2 hours free then a charge for up to 24 hours. Who in their right mind would want to spend 24 hours on a motorway service area, why don't they charge by the hour? Not that I'm in favour of paying but £12 for 24 hours works out 50p per hour, with the 2 hours free then paying another £2 for another 4 hours rest wouldn't be too extortionate, if you are on a long motorway trip this would be more convenient than coming off the motorway to find a POI (also save the extra cost in diesel). Tiredness can kill & only having a 2 hour rest isn't enough, I remember once making numerous stops staying just under 2hours before moving on I was probably more tired & more of a risk driving than if I had just carried on. Annoying thing is most of these service areas are nearly empty during the night, so even if they had limits on the overnight parking such as midnight to 8:00 am it wouldn't affect the use of the car parking.