Paul

There is little evidence [I've seen] that most masks make much (if any) difference.
Even real evidence is hard to come by, and generally refers to 'proper' masks (worn correctly).

The covid requirement has always been "a face covering" rather than a mask.
So visors have been ok to use (what real use are they ?) or scarfs, or any old bit of material.

If we were all going around with proper maks, it may have had small effect, the flimsy coverings most people have (if they even wear them properly) not so much.

Have Wales and Scotland had much lower infection levels than England in this last wave (or previous ones) with their stricter measures (inc masks) ?

It doesnt really seem so.