I dunno whereabouts in Essex you are from mate, but have you tried out Oak Lodge Fishery. Its just tucked away down a dirt track in Rayleigh (A127) its a tiny little lake, but F-Me, has it some whoppers in there! I spoke with the bailiff there one day and he said that I'd soon be p*ssed off catching the 'Pasties'... when asked what a Pastie was, he replied "oh, theyre the 18, 19lbers... they just get in the way!"
Its pretty pricey for a 24 hour session, and you do have to join, but its well worth it
link:
http://www.oaklodgefishery.co.uk/
Snippet:
Since we opened in April 95 members and now day tickets a like have fished with phenomenal results with numerous double figured Carp with approximately 80 different 20lb plus fish, 30 different 30lb plus fish and biggest to over 56lbs. The Cat fish results speak for themselves with huge stocks from our babys to 25 different 30lb plus fish, over 15 different 40lb plus fish, 6 different 50lb plus fish, 4 different 60lb plus fish, 3 different 70lbs plus, 2 approaching the magic 100lb. And of course HERCULES all 10.5ft of him!