From The Debt Advice Bureau:
Correcting Errors on Your Credit File
There is a variety of information held on your
credit report from a variety of sources. If any of it is wrong, it
could affect your ability to get credit.
Here’s how to correct the information held on your report.
The Electoral Roll
If you have registered to vote and your credit file does not show
this, please contact the credit reference agencies listed at the
bottom of this article and they will investigate the matter. If you
have not registered to vote, you may want to contact your local
authority about filling in an electoral registration form.
If you move home you can tell your local authority who will tell
credit reference agencies about your change of registration in the
course of the year.