This is what the BHF are saying about the london to southend. It should be a easy ride.
"Starting with a peaceful ride along Ingrebourne Valley, you could be forgiven for thinking you are already outside the M25, and the feeling continues as you pass through Hornchurch Country Park next. You will see the endless traffic entering and leaving the city, but you continue on a tranquil trail through Rainham Marsh, with wonderful views over the city and estuary.
Joining the Mar Dyke beyond the M25 the track, although flat, the track becomes rough and tough, before some fun bridleways bring you to Basildon. After negotiating the quieter roads through Basildon you approach the edge of Benfleet, where a medley of bridleways winds its way through the town to Hadleigh Castle Country Park, in Southend on Sea to mark the end of the ride."
what they don't tell you is Rainham fucking stinks most of the time