From UKC RAD:
"Other restricted St Bees areas:
St. Bees Far South Boulders - South of Fisherman's Steps / "Fishermans Dyno Boulder
St. Bees Head South - sectors beyond "Cryptozoo" and the cliff top access path"
So you cannot go beyond the boulder that has the Fisherman's Dyno (North), or further than Cryptozoo (at South). The description is best in the LakesBloc guide, as some of the approaches are banned. UKC is less clear because it lists different bans for sport and bouldering