In reply to Andy Manthorpe:
Depends on the sea state and which routes you are going for at Mother Carey's. The guidebook is pretty helpful - do you have it? You can get cut off quite quickly around Rock Idol - had to take an intermediate stance - and needed to be confident I could climb it!
At Mowing Word you can abseil down to access the routes around Diedre Sud at most tide states if the sea is not rough but don't do this if there's someone down already. There's only room for one pair at the bottom if the tide's in.
A good option at Mowing Word at high tide is the Cormorant Flake area. I believe you can also access Heart of Darkness from here but I've not done it.
Martin