If you are parked in a car park that allows parking for up to 23 hours, you can 'buy through' the free of charge evening period (6pm until 7am the following day).
Permit (Huntingdonshire District Season Ticket):
6 Months (Mon-Sat): £155
12 Months (Mon-Sat): £300
12 Months (Mon-Sat; 8am-6pm): £26