Like all imports - cheaper initial purchase, but:
May not be to full UK spec
May not have UK handbook/documents
May have been built some time ago and left lying around in a field for months
May have been built for another RHD market eg Cyprus, then shipped on to UK
Will not have full UK 3 years warranty
Will not be worth anything like UK supplied cars come resale
Having said all that, there are still some very good deals to be had and if you are a private buyer spending your own hard earned cash, the savings are still substantial and could well make the difference between affording one, or not.
Things like handbooks and warranty can be got around of course, but can you trust your supplier and why does the motoring trade still discrininate against imports. 'Self serving' springs to mind.
I can't comment specifically on the company you mention, but any reputable dealer should give you some confidence if you do the research.
In 2000, I bought a Euro Audi TT import from a private broker who sourced the car in the Netherlands. Full UK spec and with a pan-European 12 months warranty. Dash Pod module failed after 6 months and was replaced under warranty but when the dreaded Dual Mass flywheel issue became apparent after 11000 miles and 13 months, it was a much bigger problem and I had to threaten to go to the motoring media to get some effective redress. Yes, I saved over £4k when I bought the car, but I got my pants well and truly pulled down when I sold it on

There are still some bargains out there, if you shop around - like here for example:
http://www.pistonheads.com/sales/175311.htmWhy not consider importing yourself as an alternative

Still some savings to be had but nothing like a few years ago. Good idea if you are not in a rush to buy and feel confident enough to do the research and legwork yourself.
Cass