Sorry, I absolutely hate posts like this. The problem is you give no "qualification" as to why you think that you are good enough to be fishing for big fish, it seems "Instant Angler'ish" or Big Fish at all costs. And on a forum you are going to get stick (from me especially) as I or we don't know you personally and whether we should give you hard earned information.
You have absolutely loads of fisheries nearby to you, and all for the cost of looking up Lea Valley on Google. In fact I know a few are mentioned on here. You are right in the HotBed of Big Carp fishing with loads of waters around Hertford, Harlow, St.Albans and Watford, and many are easy to find.
not instant angler bn carp fishing 25 yrs now ,and not big fish at all costs at all i love all carp and dnt want to come across as you described . sorry if i did m8