Hollybank Caravan Park in Rixton, near Warrington is about 2 miles off Jct 21 of M6, but it doesn't get very good reviews on here. I live near it and it looks like they have done a bit of work on it over the past year and I think it may have changed hands. Would not reccomend for a long stay but it may be worth looking at if its just for a one night stop off.
One of my favourite small sites yet again - Dunston Heath Farm near Stafford off J13 M6 but I don't know if that would be too far south for you. I would do 2 night halts on your journey.
I sometimes pass Woodbine Caravan Park near Northwich. It looks quite nice by the riverside, if a little on the small side. OK for 1 night or a weekend.