50p for 2 hours? You've got it cheap up there in the north-west!
Down here in Suffolk, Ipswich charges around �1.60 for one hour but many car parks don't let you pay for just one hour. The minimum payment on many car parks is �2.70 for 2 hours. (That can work out rather expensive if you're only popping into town for 5 minutes!).
In central London, charges are much higher. For example, the minimum payment on the NCP Carrington Street Car Park (just off Piccadilly) is �13.00 for 2 hours.
Returning to Suffolk, though, Stowmarket has a policy which enables you to find change for parking. Their displayed 'parking code' states that anyone parking their car must purchase a ticket within 10 minutes of arriving. So, if you haven't got change, you've got 10 minutes to find some. The charges are also reasonable, starting at 50p per hour. The only problem is that there's not much to do in Stowmarket when you've parked your car ;-)
Chris