Thanks for your advice, i took the car to an alternator specialist and its not the alternator so im going to get a pipe and have a listen too see if i can pin point where its coming from. the funny thing about the noise is you can only hear it when its ticking over, as soon as the revs go up a little (800RPM) the noise goes, and if you leave the car standing for a week then go for a drive it takes about an hour of driving before the noise comes back