There is no screws or screw holes. Just a smooth light cover.
There is no screw cap covers, but I can see, what I think to be, two screws under the plastic cover.
I might have to bore through the plastic cover to get to the screws.
I have replied by email and included two photos.
There is two black dots showing, but the plastic cover is all in one.
No,there's no blanking plugs. The plastic cover covers everything.
I'm thinking it must be a faulty cover.
I'm very happy to leave this problem for now and not waste any more of your time.
You have provided excellent advice and thank very much.
No, but I will try it later.