VictorGolf
You are much better off getting a radar service from Farnborough than transponding to Essex that you are listening out on their frequency. I am quite sure that Essex would not blind call traffic conflicts . . . you would only hear from them if you were about to , or had, bust their zone.
It is so busy around the London TMA with everyone crammed in below 2500' that you need all the help you can get. That is why it is so great to have this new radar service (teething problems aside which appear to be nearly sorted) so don't hesitate to give them a call !
Drambuster
NB- not quite sure how far east of Stansted you plan to be, but the map can be found at:
www.flyontrack.co.uk/londonnorth.pdf