According to this Deed poll website :

"Any citizen of the United Kingdom aged 16 years and over can change their name to any name they choose simply by using their new name. This is known as changing your name by usage. With few exceptions, you can have whatever name you choose so long as you are not changing your name for fraudulent purposes or to avoid an obligation. Furthermore, there are no restrictions on how often you can change your name.

However, if you change your name by usage, you will encounter difficulties when trying to get certain documents and records changed since government departments such as the Passport Office, Inland Revenue and DVLA - and many companies and organisations - will ask you for "documentary evidence" that you have changed your name. Documentary evidence is a term used to describe a document that will be accepted to effect a change of name. Such documents are:

Marriage certificate (allows a women to change her surname to that of her husband).
Decree absolute certificate (usually allows a divorcee to revert to her maiden name).
Death certificate (allows a widow to revert to her maiden name).
Adoption order (allows an adopted child to change his/her surname to the adopted family's surname).
To change your name for any other reason than above, you need a document that provides evidence that you have changed your name. A Deed Poll is such a document and it will ensure that you get all your documents and records changed to show your new name without any problems or delays."

You can also do it by "statutory declaration" but as this involves lawyers, it will probably cost you more than the £39 it costs to do it by deed poll (on the site above - I dont know if that is a standard cost or if it varies.

Enough of the boring info - did you hear about the bloke who changed his name to "Yorkshire Bank plc are Fascist Bastards" - and when he closed his account with them, they had to make out the cheque to him in that name!

Bagpuss