PCInk - 9:19 am on Sep 2, 2009 (gmt 0)

If it's a large UK international retailer, they are probably a limited company. Their company name should end in 'Ltd' or 'PLC'. First step is to ensure that they really exist, or still exist since many companies have gone under in the last year or so. Limited companies can be checked on www.companieshouse.gov.uk. It's not a comprehensive check by any means, but it is a start.