like mrspnut I did a lookup (you can check .uk domains at either www.nic.uk or www.keepyour.co.uk which are both run by Nominet, the UK domain authority). Details showed the same address as shown on the "about us" page on the website.
Domain name:
katzwhiskas.co.uk
Registrant:
NYSC
Registrant type:
UK Sole Trader
Registrant address:
8 Rawcliffe Avenue
York
YO30 5QD
United Kingdom
Relevant dates:
Registered on: 04-Feb-2002
Renewal date: 04-Feb-2010
Last updated: 02-Mar-2009
Registration status:
Registered until renewal date.
Name servers:
ns1.maximumasp.com
ns2.maximumasp.com
WHOIS lookup made at 15:28:41 17-Nov-2009
If a domain is .com .net .org or .info you'd need to search elsewhere (generally I'd suggest starting at www.internic.net )
One thing to watch out for, however, is where a stupid website designer has put the registered address as their own (designer) address. Some do this to 'hold to ransom' the real business. It's unprofessional, in my view, to do this, as well as there being a 30 quid fee for making changes at Nominet (and sure enough, it's rarely the damn website designer who has to fork out the fee to show the correct business details).