Ian,
Luckily only one screw was seized, and my previous attempts with
incorrect drivers knackered the head. I had to drill this one out. An ezi-out may
get the piece out later.
After some mis-ordering, it's a PH4 that fits. I've no idea how a PH head
found its way onto a Lancia, but there you go!
Screwfix have perfect Allan-headed A2 countersunk screws as replacements for later,
although they'll have to be shortened for the bonnet connection.
As for ULEZ, I think you'll be able to check the website before venturing outside.
Nigel