as the AUK entry for the Kelvedon Oyster doesn't give the org's email address, I post the following here.
As part of a DIY 200 (sadly, I cannot to the Oyster, as the weekend does not work for me) a few friends of me and I today rode parts the route - the bit between Colchester and Maldon. It's a really lovely route, but there is one short bit which is a bit unimpressive. Approaching Tolleshunt D'arcy, the track leaves the main road and goes on a path/bridleway which is either unpaved or full of gravel. Really not ideal at this point of the year. We stuck to the main road, which adds maybe 500 meters but is much nicer to ride.