Shower panels

[jackg]

Fitting a ground floor shower room.
Shower tray is 1200 x 800 with four upstands, tray is recessed into scree by 30mm.
Studding on three sides.
The studding was installed before the tray so 20mm thickness of wall is required to overlap the upstands as I could not cut the scree flush with the studding.
So advice is needed for the thickness of the panels, 10mm or 6mm? and the substrate as well. Considering using Marmox or similar.
So if 10mm panels are used then minimum of 20mm thickness of substrate needs to be fixed prior.
Could 19x38mm roofing battens at 90 degrees to the stud be used with the panels on top of the battens?
Are right angle end pieces used where the panel ends and the plasterboard begins, where the enclosure screws to the wall?
Thanks for any help

 

[foxhole]

I used 8mm plastic walling in one shower but needs backing to prevent flex, in other shower used 11mm laminated ply which is rigid enough on it's own.
End and corner trim available and also upstand to keep everything water tight easily.