In reply to Fatclimber:
Swanage greasiness is usually caused by humidity and condensation from the sea. Ironically, during the summer, the lower cliffs tend to suffer from condensation. This is because there is more evaporation caused by the higher temps and then condensation on the cooler rock nearer the water. It usually gets better the higher up a route you get, but low down can be a problem, particularly on crags such as the promenade and Palace of the Brine and Subluminal.
An onshore breeze often reduces the problem, though can then increase the swell.
Rich.