In reply to 1philjones1:
Double yellows, where present, apply to the "building line", even private land (so the "rock line" in the case of the layby in question, if I'm Google Street View-ing the right one). I've heard of a few businesses in London being caught out by that - if you want to park on your own property the road side of the building line, you have to wall it off and get a dropped kerb installed.
It is a bit entrapment-like not to put signs up saying that it is for loading only, though.