Fearful noise from under bonnet of 318 (08) when driving at speed
 

Hi. I'm new to the forum, so Hello to anyone who reads this. Problem is - can anyone help? - I have a 318 tourer on an 08 plate (petrol, 4 cyl), and if driving for a while at 95-ish (okay - I know, I'm breaking the law), it develops a horrible grating, rattling noise from under the bonnet - you'd think the engine was about to fly apart. Scared the s**t out of me the first time. Sounds like it's from slightly forward of just under the windscreen. The sound dies away slowly after slowing down and the car is then fine on minor roads. Then the racket kicks in again when back on the motorway at speed. Any suggestions gratefully received. P.S. I will be going slower now until this is sorted - I don't have a death wish!! Thanks.