Love the Stiffkey site, been there about 4 or 5 times not as a cycle tourist but did take a bike the last time we went and had some lovely rides. The site has a nice balance between good showers, washing up facilities, sale of gas bottles but that's about it which is just right for us plus it's within walking distance of the pub and the small shop. It does get busy on the weekends but as somebody else said I think they'll take walkers and cyclists (I think there is a spot they keep for them near the entrance). It's right on the coastal path and within easy walking distance of Wells, Morston and Blakeney.
I think North Norfolk might be my favourite spot in the UK, massive expanses of beach (great when we had our lovely spring spaniel, Rolo) some great walks along the coastal path backed up by an excellent bus service so you don't have to do an out and back and it drops very close to the campsite at Stiffkey. Blakeney point is a good walk but really lovely.
Hope to get there this year.