I think the car park entrance is a lane on the left, but are we talking about the same place, behind the toy shop?
Yes, my mistake. Pay-and-Display carpark entrance is on the left, behind Toys'R'Us.
Exeter Street was cheaper last I knew, but not as well lit, although the takeaways meant it was quite busy. Turn left at the lights into Dereham Road, drive past the pub and the Jet filling station, then turn right by NICE. Sometimes you can get one of the free spaces beside the car park.