As a spare set you could clean the inside of the Broken
handle and make a new part out of Liquid Metal that will stick to the handel then drill and tap to fit the bolt
G
It looks to me as if the screw that looks like a door stop goes though the inside door handle and screws into the white part that’s broken of the outside handle
G
A belt sander is what you want there great for getting in small areas
I use to repair bus chassis like putting air bag mounts on chassis etc
that is a tight job to do and belt sanders was your friend when grinding and cutting the old plates off .
G
Sorry to read about the mot fail but knowing you you will get it jacked up and repair the rot
Dont forget fuel pipes melt
a friend of mine found this the hard way and passed away
G