bw100 - 6:51 pm on Jul 9, 2011 (gmt 0)
You have to provide the personal details to the registrar. To hide them, you can add a "Private Registration" option (for an additional cost). This will result in your personal information not appearing in the public WhoIs directory; instead, the name, postal address, telephone and fax numbers and email address of the "proxy" registrar will appear.
You might wish to check with your registrar(s) of choice re whether this is available for .co.uk domains. There are apparently some domains where this type of feature cannot be used due to registry restrictions.