Anyone who creates an original work automatically holds the copyright in that work. (There are certain exceptions, particularly related to works created in the course of a person's employment, but they don't appear to be relevant here). Consequently there's no system for registering copyright.
If you're seriously concerned that someone might infringe your copyright there are various ways of providing yourself with some protection. One of the simplest is to photograph your work and post the pictures to yourself, in a sealed envelope (of a type which can't be opened without it being obvious that the seal has been broken), by recorded delivery (and, of course, retaining the dated proof of posting showing the tracking number of the letter). In the extremely unlikely event that you ever had to produce evidence that your work was produced earlier than a subsequent copy, you could produce the (still sealed) envelope bearing the tracking number, together with the proof of posting to show when you put it in the mail.
http://www.ipo.gov.uk/types/copy.htm
Chris