Hi folks, your help please

Ive got a really annoying rattle that sounds like its coming from the dashboard area, almost from within the air vents. However, adjusting the fan/air con settings has not effect on the volume or tone o fthe rattle.

It normally happens above 40mph and always above 60 so cruising is a right pain. Even the stereo doesnt completely drown it out.

Ive tried a search and investigated everything I can see from that. Ive taken out the glove box (easy peasy, 5 screws plus the lamp connector) and its out and had a look and a feel around but cant seem to be able to pin point it and stop it

Any ideas

Open the windscreen plenum (left side only) and look under the pollen filter.