There is Granary Wharf, where you can park under the arches, and is manned until late, and patrolled during the night. It used to be £12 per day (24 hours) which was not that long ago. These arches are fully refurbished and are well lit
You can also park in the Dark Arches under the railway bridge which is cheaper and looks secure, but less inviting in appearance.
Both are just a few minutes walk away. There is also a multi story car park near the station entrance which when full overflows into an open area car park.
Rail travelers get discounts, but I am not familiar with the cost.