OS Explorer map 197 coordinates 2844 for Waldringfield. Hemley is just a little to the south of that.
I can get around Waldringfield and Hemley in about an hour but I always have to stop and look at the boats near the sailing club, especially very early in the morning when there’s noone else about.
From BT Adastral Park ride alongside the A12 (please don’t ride on it, very bad idea), past the Brightwell bus cafe, turn left and follow signs to Waldringfield. Ride through Waldringfield until the road runs out and you hit the river, right by the Maybush pub. On the the way back turn left towards Hemley, go past the church and up the hill. Follow the road around a sharp right without going straight on into Hemley. Keep on past the Newbourne Fox then turn right and follow the road back towards Adastral Park which is a very useful landmark usually visible in the distance.
Distance around 11 miles.