I have found a couple of Caravan Club CL (Certified Location) sites listed in the CC sites directory. These are usually just fields with a water point and elsan emptying facilities, although some do have loos and electrical hook-ups. They are usually quite cheap £5 or less. Officially they only allow CC members and are restricted to a maximum of 5 pitches, but many that we've been on don't enforce these rules strictly.

West Marsh Lane, Barrow Haven DN19 7HA. Tel: 01469 530331 £5 map.

Soff Lane, Goxhill DN19 7NA.   Tel: 01469 530644 £3   map.

I haven't managed to contact either of them yet.