There is probably a 3 hour limit at ASDA.
It appears that you can pre-book a space in the Furnival Gate NCP for £4 for the day. 10 minute walk from ground.
Had a quick look into this (there’s a thread on their NSC equivalent) - apparently can take forever to get out of the car parks after the game (over an hour cited). Got a justpark driveway space 20 mins walk away (in the right direction to avoid some traffic) for £4.