Wetroom - is my shopping list right?!

[Qwerty]

James, I would say no I'm afraid. Point loading on the former could cause serious issues.

Also, the adhesive needs to be between the backer boards & substrate. And please, please don't use chipboard. Get some WBP ply (min 18mm) instead. Apologies I didn't pick up on that yesterday, only just realised you mentioned chipboard

 

[Impey Showers]

We'd love to see the glass mosaic finished result.

 

[SJPurdy]

You can use mosaics on the floor but not over the decoupling membrane or the insulation board.
I'd suggest from the top down:

mosaic
adhesive (good quality cement based mosaic fix)
SLC (good quality and stated as suitable for over UTH)
UTH
6mm "no more ply" (or similar) tile backer board glued and screwed (and primed/sealed)
18mm exterior grade ply (sealed on back and side edges) and screw fixed at 300 c/c max. (extra noggins may be required)