Bid Increments are a standard part of eBay bidding. We have an explanation of Bid Increments in our Tips section of the site, here
For the specifics of bid increments on eBay UK, please see eBay http://pages.ebay.co.uk/help/buy/bid-increments.html
Note that the increment amount rises as the current bid price goes up, so the higher the priced item, the larger the bid increment required to have eBay accept a bid.
If you have any further questions after taking a look at the above links, please feel free to file a support case from under the Help tab of the site and we'll be happy to assist you further.