Ok - I'm still working on my dash at the moment (I'm swapping from a brown to black interior) but here's a picture of the grill just resting in place. I've held it down to the dash and it fits nice and flush and will be fine when bonded.
If it generates sufficient interest I might bang a few out on ebay and see how they sell.
All comments welcome as to how I might make it prettier.
Obviously it'd not look so good if your dash has cracked AND warped like the Himalayas
As far as I'm aware it'd fit both left and right hand drive cars up to 1985 /1