There should be some info about this, on the site you bought from, when you registered the name.
If not try looking in your Control Panel for something like this:
UK Whois Privacy
From December 1st 2002, Nominet, the registry for UK domain names, has made registrant address information public for new registrations and renewed domains.
This means that when you buy a new domain name or renew an existing domain name, your address will be visible on the publicly available Whois server.
The UK registry, Nominet, allows you to request that your personal contact details remain private and are not revealed on the whois server. If you wish to keep you contact details private, please select 'private' from the drop down list below, else select 'public'.
That's from the Easily site where my names are registered.
Once you find the page and activate your privacy it's then in the hands of Nominet and will take up to a week to change.