Vauxhall Vectra B facelift - 2 Litre diesel - johig

Hi I have a Vectra 2 litre turbo diesel. the engine loses power when the temp rises to normal running temp on tick over the engine surges took to main dealer and they told me that the fuel pump module had gone cost £200 but have to replace pump also cost £800 it did this about 12 months ago for about a fortnight then cleared and has been fine until now any ideas