You've reached the same conclusion as me. A single lens when wet/humid and glasses when dry.
I think it is possible to have the lens in the wrong way round. Be careful to keep it the right way up as you take it out of the packet. If unsure check it is bowl/dish shaped on your finger as opposed to more like a plate with a flatter curve. Not that I'm an expert. Far from it.
Is Merthyr on RG?
Chas is right .
If it's inside out it "swims" all over the eye, & each time you blink it swims. it's pretty obvious when in the eye; you'd know.
Where's Merthyr mawr then?