Essex is a short hop to London, Lucas. There are Sunday bimbles, usually, which describe a circuit of London, commencing from Wellington Arch, at Hyde Park Corner (Google is your friend).
Check out the FNRttC thread, or the blogspot, which will give details of 'Weirwolf Rides' (don't worry - that only applies to the women who do them) to the Coast - be it Bognor, Brighton, Southend, Whitstable or Swansea - who knows?
As Becs mentioned, there are many who could hightail it to, say Brentwood, meet for a ride and disappear back to London. Some of us have been known to 'disappear' all night long! (But that's Andy and Dave's fault - my error has long since been forgotten)
The North Sea is nice - but unwelcoming.
Read 'Sunday London Ride' to get a flavour, and sort yourself out. This Sunday is a 'special' for a CycleChat member from St Louis, Missouri - he will be pleased to see you!
Edit: 'i' not 'a'