Rattle behind the Touring identity plate on the bulkhead

[FERGTS246]

Hi, I've got an incredibility annoying rattle coming from behind the Touring identity plate on the bulkhead when my foot is taken off the accelerator pedal. There seems to be a void behind the bulkhead and I can't see how one would gain access to it. I can't see any access under the dash and the only possible access I can see under the bonnet would be taking off the thin 'U' shaped aluminium trim that covers bulkhead upper lip and flat painted panel upper lip - see pink arrow in image attached.
However even if I got the trim off I don't think I would be able to part the bulkhead and painted panel to gain access.
Anyone got any ideas for gaining access?
I could take off the Touring identity plate, cut a hole where the plate was - but that seems a bit excessive.
Thanks
Chris

[FERGTS246]

I found the noise was coming from the vacuum check valve. The rubber seal in the valve wasn't seated properly. Corrected that - the noise has gone.
Chris