Lechlade seems to have a very big head of doubles and near doubles, particularly browns. I've not fished it recently but it seems a bit patchy in terms of fish location. If you get it right, you can really have a day to remember!
This is good up to date info:
Lechlade update
The quality of fish at Avington is superb with plenty of stockies between 5lb and 8lb and there are several big doubles in each lake. I'll be suprised if there have been less than 20 big doubles out in January, even taking into account the atroious weather early on. The big challenge is to locate those doubles in these low light winter conditions. The weed levels at Avington are at the lowest at this time of year so there's a lot more clear water to stalk. If you can get a bright fairly still winter day then stalking will be brilliant. If the weather is a bit tougher then fishing blind will get you your limit of superbly conditioned fish fairly easily (usual caveats apply!).