We have a 900x900 shower and it's plenty big enough. Neither of your proposed layouts looks that great, to be perfectly honest, sorry! In the first layout, you could improve it quite a lot by swapping the toilet and vanity (centre the toilet under the window on the bottom right of the picture if possible), and having the shower door on the other wall (beside the door). Then, you could have a towel rail on the wall beside the door (i.e. behind the door when it's open), which would be accessible from the shower but hidden when the door was open. An 800x1200 shower might be a good size for your space. You'd have to choose a toilet that doesn't protrude too far, plus a narrow vanity. With that layout, you could have a long but narrow wall-hung vanity, with a big mirror covering the wall between the windows, which would make the room feel bigger and would give a good amount of storage. Also, you may find this helpful: http://www.houseplanshelper.com/small-bathroom-floor-plans.html?utm_content=buffer4aa20&utm_medium=social&utm_source=facebook.com&utm_campaign=buffer

I am trying to source (in New Zealand) a shower tray which will fit into my alcove Sized 1900x1000 for the shower. Thus far for that size (and I have searched online and in merchants) found only tiled over solution to completely cover floor space. Not totally happy to have this as feel that tiles will be slippery when wet. Whereas have found smaller acrylic trays that are described as non slip even tho they are smooth. Can anyone suggest a supplier that they have used for trays and hinged/pivot doors of the size I require? Or if place a shorter acrylic tray to the length (probably 1200mm) of the glass wall, as will create a walkin with what do I cover the remaining 700mm of the alcove floor? The bathroom floor will not be any kind of tile, more likely to be a textured vinyl plank.

seeking information and specs on black window/door manufacturers that would work in multi-seasonal house

My comment would be that fluted glass would be a bit harder to keep clean??