I just discovered a week ago that they sold my email address to ukdata.com (I know because I set up a specific email address for companycheck, and that is the one that I got spammed from ukdata). Their privacy policy says they will never share your data, but that is clearly a lie. I contacted companycheck a week ago about this, but haven't heard back yet ("We aim to reply to all customer queries within 1 working day, and all non-customer related queries within 7 days"). It's pretty crappy customer service if you have to wait over 7 days for a reply, especially for something that is a major screwup on the part of companycheck.