[markwilliamson2001]

Well you have a couple of options IMO...
The most popular cars at club level seem to be Team Associated B44's and Schumacher Cat SX2's, mainly as most people run them, and parts are available from a number of UK retailers.

You do have some other options as well, but there are downsides to them in my opinion.

Three Japanese cars: Tamiya 511x (belt) or 502x (shaft), and the Kyosho as mentioned by roger.
All these cars are very well made, but they are dearer to buy, and parts are not quite as readily available in the UK, but the Kyosho seems to be gaining popularity, which is good. The Kyosho uses a better designed and more reliable, but less popular wheel fitting (12mm hex). For my next 4wd, i might even consider the Kyosho, as it seems to improve upon my niggles with the B44 (like adjusting the inner ballstud height - annoying, as it means taking the front top deck off to change easily).

Yokomo b-max (whilst good value in the cheaper models) seems a bit less popular, not too sure why, but it hasnt caught on as much as I expected, even after winning a National.

The durango is good value in the 410R version, but uses fluid filled gear diffs, and opinions are mixed as to how easy it is to drive, especially if you race other cars with conventional ball diffs.

The other option is to wait a little, and see if Losi produce a new 4wd buggy, alongside the recently released 22 2wd buggy.

Personally I run a B44, which I bought cheap 2nd hand.