Reckon there has been a thread about this recently but here are three off the top of my head:
- Hadston Carrs (here) is right by the beach south of Amble. When driving from south on A1086 coastal road it is a sneaky right turnoff (no sign post) 3/4 mile after the Druridge Bay Country Park one. Its probably not on the site's POI because officially you're not supposed to stay there overnight, but everybody does.
- The fishing village of Boulmer (here - sorry Google photos taken on rotten day) is very welcoming to campervans - even has a well kept public toilet and you'll be even more welcome if you frequent the village's excellent pub. If you've got the legs for it, its a great walk south along the beach to Alnmouth.
- Just north of Bamburgh is a layby along Budle Bay (here) a nature reserve for wild water birds just south of Holy Island (where you definitely cannot stay overnight).
There will be more on the POI but these are all personal recommendations. Enjoy.