Coming Cash Crisis

EU members cannot agree on a budget and it got me thinking. The budget in question is for the period 2007 to 2013. It was possible that agreement on this budget could have been achieved earlier this year prior to the UK General Election. So imagine the scenario. A budget is agreed to up until 2013. The Conservatives win the general election pledging to reduce Britain’s contribution, cut spending on CAP or some other issue that would impact the budget. The Conservatives lose the election in 2010, having spent 5 years in power, with a budget that they were fundamentally opposed to, unable to change anything. 5 year Budgets are common in communist countries of course, but failing a revolution the government is not going to change anyway. But how can a five year budget be reasonable in a democracy where priorities change and governments can fall. How does any British Government have the right to tie a future Parliament to an EU budget that they may wish to change?