Hi Magnet, Thanks for commenting. I had to drive my car today 70 miles the noise was not apparent ongoing but just when turning on the engine and going slower. I know the belt is tighter because pre garage visit- I took off the casing to see the cam belt - I wiggled it and it was more loose. On hearing the change in sound - rechecked under the casing and the cam belt is definitely tighter. I asked the garage after changing the bolts if my cam belt was OK and they did not say they had done anything to it. The independent garage specialise in audi and use genuine parts. They seem to have a good rep. The water pump is on the opposite side on my 1.4 petrol engine I am told. I am thinking of going back tomorrow to ask them about it. (Noise).