Great Britain is one of Europe's largest economies, rivaling Germany and France in terms of economic output. There is no reason why the United Kingdom can't afford to pay Europe a little more into its annual budget--it will help shore up the EU's economy in general. The UK already isn't part of the Euro zone, so the least it can do is prop up its fellows with an influx of more pounds Sterling into its neighbors.
No, Britain should not give up its annual rebate on its payments to the European Union, because Britain made a business decision when it decided to lend the money, and Britain has no obligation to give charity to the rest of Europe. Britain should receive the benefit of its business deal.