Having seen plenty of UK accessories I'm pretty sure the the picture in the OP shows the back of a faceplate made from formed sheet metal. The thin edge, along with the lack of reinforcing ribs are the giveaway.
It does seem to have some kind of black finish on it, but generally we do not regard paint/finishes as electrical insulation as, even if non-conductive, they are too thin and easily damaged.
Yup, many things are possible and the electrical industries and regulations in different countries clearly went in different directions. In practice, unless you want to 1. pay a bunch of money to import stuff and 2. Be left with something that is a PITA to maintain and repair, you have little choice but to use what is sold the country you are installing in.