Personally I would look for something from ebay. Although I don't have any first hand experience of either of the buggies you have mentioned, I know you would be able to get a more 'recognised' brand for about the same money if you bought second hand. The problem with getting a Carson or XTM would be aftermarket parts. I imagine that you would be stuck with manufacturers hop ups as your only option with these brands, a HoBao hyper7 for example, would open up a whole world of aftermarket brands and would cost about the same from ebay. Have a look around, there are some real bargains to be had.
Just had a quick look around and £200 will get you a long way on ebay. There is a Kyosho MP777 starting at £100, a GS Storm going for £72!! or the piece de resistance, a CEN Matrix RTR for BIN £207 (minus shipping).