In reply to Wan: You don't need to worry about tides at Kenidjack Main Cliff. It may be affected by spray if the seas are rough, but I don't believe the sea will be rough this weekend.
There is a surprising amount of non-tidal climbing at Chair Ladder, including one of the routes recommended earlier, Sea Horse, which is not at Sennen.You can use the East Chimney descent to access South Face Direct, Pendulum Chimney, etc.
Conditions are extremely favourable at the moment - most cliffs are very dry. If you are a fairly regular visitor to Cornwall, then I would suggest you try something which would normally be wet - my tips would be
Light in August (Whirl Pool Buttress) - scramble down the ridge, run across the sand, climb the route. Watch out for the grass cornice on pitch 2.
My Mule Don't Like You Laffin (Carn Vellan) - some brittle rock but a great outing. Could be combined with an ascent of The Dungeon.
This Saturday, 28th September, low water is about 3:20 pm at Cape Cornwall.
Hope this helps