You may already have heard about this, (I hadn't, as it happens), but from early next week all UK mobiles will be put on a directory which will mean that anyone will be able to access the numbers.
It’s easy to unsubscribe but it must be done before the beginning of next week to make sure that you are ex directory.
You may want to suggest it to all your friends and family who have UK mobiles or they could be swamped by unsolicited messages and calls. Removal is recommended by the BBC - see link. (I recommend reading this first. Sue).

http://news.bbc.co.uk/1/h[...]621.stm

To remove your number click on the link below. (You need your mobile phone with you to do this as they text you a code).

1) http://www.118800.co.uk/


2) Click on ‘Ex Directory’ at top right hand side of page, and from there it’s apparently straightforward.

N.B. I have not done this yet myself, service is temporarily suspended (Sat 11th 15.00hrs).
I suspect it has been overwhelmed by requests!