I'm a little bit iffy in worrying about 'having to catch a 30', but that is just me, possibly because I don't know your ability level, and knowing how few and far between 30+ fish it has taken me with over 30years fishing experience, only ever catching 3 30's.
Suffolk is pretty much a no, although NS fisheries, West Stow and Nunnery may have space, although very much a case of what you know (have a look at Suffolk Venues)
I can point you directly to Lee Valley fisheries, and they are not syndicate. They have venues from the edge of London to Harlow, Broxbourne and Hoddesdon.
Nazeing Meads has 3 lakes, Brackens, which has a few 30's, 2 acres, but quite a hard 'riggy' water, where the fish can shy away from pressure, or the Lagoons, which I know hold 30+ fish, although I have only managed to get to 27 so far from there.
http://www.visitleevalley.org.uk/go/fisheries/
There is a gallery on each fishery as far as I can remember, and a few of the fish may look familiar