30p makes it seem pretty clearly an attempt to discourage locals from occupying all the parking spaces for extended periods, plus maybe encourage some who live in the town to walk or cycle into the centre instead of driving, rather than any attempt to "fleece" visitors.
Point1: That is the reason the council has cited for the parking chrages. Now this would make sense if the local populous or visitors were struggling to find parking spaces. However, the truth of the matter is that they are not. Even when they were free parking, there were always loads of spaces at any time of day. We do not have a multitude of commuters as there are no large employers in the town centre. The largest employers are retail outlets and the post office, which are sited out of town and have ample free parking for the employees.
Point 2: I am all in favour of anything that encourages walking ./ cycling instead of driving, as Rasen is not immune to the car-centric types. However, given that the biggest draws are the retail outlets and supermarkets (which have ample free parking for patrons), rather than the town shops, I can't see it having any significant effect.
Point 3: The town is struggling to encourage trade from outside, and free parking was seen as an attractive persuader for capturing passing trade. However, many traders in the town feel that now, you can pay a similar amount to park in bigger nearby towns that have a much more varied and comprehensive shopping experience, that shoppers will go there instead.
I also seems that Rasenites as a whole are stingy as since the parking charges have been imposed, the car parks are empty and there are cars seemingly ambandoned on the streets in some quite frankly appauling attempts at parking.