So having got some lights I have been out doing some evening rides and found out one of my local bike shops run a regular wednesday evening ride. thomas revolution in colchester
http://www.cycle-revolution.net/the shop is based in colchester but it sounds like they often head further afield (danbury has been mentioned tonight).
the group leave the shop at 6 and aim for a 8:30 return.
ride location is decided each week and if you ring the shop on a wednesday afternoon they can tell you when (and for those coming from south essex and wanting to meet at the ride spot rather than the shop - where).
if i can get out of work early today i shall be giving it a go and in the future plan to work from home on a wednesday to make joining the ride easier.