Morning

It’s very hard to say as we had synthetic thread in this country before we had rationing in WW2
Personally I don’t think you have anything to worry about if the badge glows. Although I don’t believe synthetic material was used in the badge you have shown tbere are many reasons why it might glow
From what I have heard other collectors say the idea of a badge being wrong if it glows under UV light is a little outdated

Regards
Geoff