The more I think about this, the more I actually believe it is a good idea.
It is a real pain when you have to pop into town to do something quickly - go the post office, dry cleaners, pick up a birthday card etc. and you have to pay 80p when you are only going to park for 10 minutes or so. So that has to be a positive and will encourage people to use in-town shops when they want to be quick, rather than going to out of town stores.
I can't see that the £1 at night charge is going to have a negative impact. People already park on the single yellows, it is illegal to park on the double yellows anyway and those will be enforced (as they already are), and the £1 charge in the car parks will off-set the lost revenue from the free half hour period earlier in the day. I can't see that it will stop people coming into town to drink / eat etc.
The only downside is for in-town residents, but if you choose to live within a city/town centre in a place without dedicated parking then it is always going to be an issue and is surely something that one takes into account when choosing to live in the centre (as I have done previously).