Although I am in the US, (and was a Copyright & Trademark attorney for 11 years) copyright law is almost identical in the UK thanks in part to the Berne Convention. Artwork is automatically copyrighted but you may wish to register it. This is the information you will need to register your work as well as the other methods for protecting your work.
http://www.ipo.gov.uk/copy/c-claim/c-register.htm
If you have any other questions let me know

