As someone from the UK, Techy, nerdy people can know, but normies don't.
Also, I'd add that gym bros definitely have heard of them, especially if they are familiar with steroids.
The GLP-1 drugs are probably the main cause of this. We have this amazing class of compounds that work really well, But are priced pretty high, at least considering lower UK wages.
So there is a big incentive to look at getting these much cheaper from China. You hear about this happening, and then you see the fact that these companies have big catalogues full of other peptides that are a crypto payment and a click away.