I had a shower tray fitted (badly) and it is about 10mm out from the wall all round. I have fixed the gap with silicone and tile slithers to bridge the gap and tiled down onto it. BUT.... I now find that the shower screen will not meet the wall even with the adjustments allowed. Would it be possible to attach a plastic strip behind the wall bracket, with screws and silicone, to compensate for the gap, or do you have any other ideas?
Show pics of your set up. Wall Chanel extensions are available for some designs. Wall profile extension kits from Vic plumb for instance.