Never used them myself, however my brother in law has got his last 3 cars from there and never had any trouble and is genuinely pleased with the service they provided.
Only thing to watch out for us that some of their cars may be imports, so you should specifically ask the question about any car that takes your fancy. I phoned them a couple of years ago about a Seat Leon Cupra and it turns out that it was a Dutch import, so that put me off.