This website Companies In The UK does not represent the official register of companies, and this website is not affiliated to or endorsed by Companies House, the UK government or any official body.

The official register of company information in the UK is Companies House.

Companies House receives a lot of criticism regarding the accuracy of its data.

As noted in this article by the Guardian newspaper:

no one checks the accuracy of the information you provide when you register with Companies House. You can say pretty much anything and Companies House will accept it.

In fact, Companies House mention here:

The fact that the information has been placed on the public record should not be taken to indicate that Companies House has verified or validated it in any way.

The Companies In The UK website attempts to address the short comings of the official Companies House register by cross referencing and enhancing the raw data from Companies House.  

For example, on the Companies In The UK website you will find mentions of the company in The Gazette, the company's Website, indications when many companies are registered at the same address, better search to find related companies and many more features over and above what the official Companies House website is able to offer.