Hi, just bought a low mileage 22k 1.6 HDi 307 56 plate. Now not had a diesel before so not sure if this is normal. On start up or switch off of engine i get a knocking noise (just a couple of knocks) mostly when car is warm, nothing while driving (i think), sounds like its from under /front of drivers seat. Any ideas? Exhaust or mounts? Just been through an MOT yesterday all fine?