Sorry Bill, only just spotted this. I'm Bexley/Sidcup borders too and have just got back from a round trip to Whitstable with
@ianrauk of this parish. It was a 110 miles, so possibly not the best one for you to start with! Keep checking the Sunday London Ride thread - I'm going to put a call out to see if we can get something organised for next weekend. The SLR is a social ride, at conversational pace and will involve cake. But if you add in the ride up to town and back again, you can expect around 40 miles. Cheers.