I've got a couple at the moment.
One in the front roof light and one behind the right centre vent.
Push, squeeze, prod, poke and pull anything you like they won't go away!
I did have one behind the dash in about the same place as you describe exforces, and after loads of searching I found it by accident one day UNDER THE BONNET
It was the FBH exhaust knocking against a post on the wing.. Did the bolt up and hey presto, gone and never returned
It's amazing how the sound can travel.
Regards. Steve.