a .uk.com address is always a bit worrying. It's actually just a .com address but .uk has been included within it to make it appear as if it's UK-based.
Any genuine UK-based web trader MUST (by law) provide a postal address. As Sandy points out, that website only provides an email address.
Actually, looking a bit further into the site, it actually states that it's based in China:
http://www.armaniwatchescenter.uk.com/about-us
If you buy from that website, and your order doesn't arrive, you'll have no way of getting your money back.
If your order arrives in this country, and HMRC identify the watch as a fake, your watch will be seized by Customs officials, without compensation. (Theoretically you could also be prosecuted for attempting to import counterfeit goods).
If your order arrives in this country and HMRC treat is a genuine product, you'll have to pay the following charges (based upon a $260 purchase, equating to £167.26):
Import duty (4.5%) = £7.53
VAT (on £167.26 + £7.53) @ 20% = £34.96
Customs examination fee = £8.00
Total = £50.49
Chris