a full recce yesterday, which I found surprisingly hard work, made harder by an hour and fifty minute wait for the ferry at Harwich. No surprises, just full on enjoyment.
Strip everything off your bikes that you don't need. Absolutely everything. You don't want anything taken out of you on the hilly bit at Brentwood, and I don't want to have people waiting at the top. Remember also that you have to carry your bikes quite a way on this trip. Be really careful about your clothing - it needs to be light, but you need flexibility. And pray for a following wind.