We used a TrustATrader listed company who turned out to be operating in a very dubious way. They came across as all nice and pleasant when dealing with them and also did an all right job, however they used very calculated tactics all aimed at extracting maximum profit of us. We saw through them and they then revealed their ugly side. I am fully convinced that there will be other customers who did not come to that insight, and to them these guys might look like almost saints deserving glowing five star ratings. Just to be aware!
The way TrustATrader deals with complaints (14 day hold to give the company a right to respond) means that you negative reviews rarely end up at the top of the review list. Positive feedback seems to be posted more or less the next day.
If a cowboy trader is clever at their deceits, then they might still end up looking good on the site. Compare prices and go with personal recommendations instead. Don't buy on the doorstep and pay upfront.