I know its not the end of the world issue, but it is annoying when the surround keeps falling off when the door is closed.
After 10 minutes with a rotary tool i removed two of the lugs on the surround that hold it in place, then bored out two holes to accommodate the screwheads, now two screws hold them in place:
I don't know why the normal clips don't hold its not as if they are broken and everything else was fitted correctly, i think though with age the door card has swole a bit round the handle and puts a bit too much pressure on the surround so it keeps flinging it off when the door is shut it only seemed to affect this door mind, all the others seem to be ok.
As for a concealed screw it would be impossible to do it, unless an even bigger hole was bored out to accommodate a screw cap, but then getting screw caps off is tricky, the black screws used were the ones that hold the outer window seal in place they are just the right size and colour for the job. The right one isn't as neat as it could be ill need to angle the screw in a bit more so it sits flush with the surround. Although two screw heads look tidier than a big gap.