That's my guess too, Tom T. I've had a quick look at the site and they look like a car booter done well and grown to a sustainable level of wholesale. But whether that's by fair means or foul, I could not possibly comment.
Your best route, may I respectfully suggest, is to see what you can find out about them. It may be a real gem, so don't shout about it. Do a WHOIS on the web site - but that won't help because they openly state it's on shared space and a subdomain, look them up on Companies House to see if it's a registered company, follow up on any claims they make in their "about us" section then, if it still looks reasonably good, test them with a few small orders.
In other words, do your own homework as expressed in very many threads and stickies all over this site.
