I have an AEG Competence electric oven. Yesterday we noticed that the fan was still going hours after we had turned off the oven. I switched off at the plug and left it all night. When I switched the plug back on this morning the fan started immediately so I'm assuming we need a new fan. Is this a DIY job? Roughly how much would a new fan cost? Any idea of how much a technician might charge to do it (inside M25 ). Any other advice would be most appreciated.