How about something bang in the heartland of Mid-Essex? Felsted, Gt Leighs, Terling, Lt Waltham, Littley Green (if going past the Compasses doesn't make you too sad) and back to Felsted (from my perspective starting in Dunmow). About 20 miles, depending on how many wiggly, laney bits. Easily accessible from Chelmo, Witham etc, goes past Rob and Josser's front doors and could be stitched whole or part into any longer evening ride you might fancy?