How to rebuild a 1930 bay window box

[JWFisher]

Hello!

I'm currently removing a rotten bay from the exterior as the render has failed and the laths behind are totally rotted through.

1. Does anyone know what the black sheeting is called and what the modern version is called these day? That's failed and needs replacing too.
2. I'm planning to batten, board and wrap in breather membrane, but what's the best order to do this before EML is used for the render?

Thanks in advance

 

[Notch7]

From inside:
Foil backed plasterboard
Vapour control layer
Studwork with insulation
Plywood sheathing
Breathable membrane
50 x 25 battens vertical
Render carrier board

https://www.sts-uk.com/sts-construction-boards-collection/sts-construction-boards-6mm-9mm-amp-12mm

 

[JWFisher]

From inside:
Foil backed plasterboard
Vapour control layer
Studwork with insulation
Plywood sheathing
Breathable membrane
50 x 25 battens vertical
Render carrier board

https://www.sts-uk.com/sts-construction-boards-collection/sts-construction-boards-6mm-9mm-amp-12mm

Thanks!! Appreciate the help. Do you know how I re-create the curved sections and the rotten underneath as shown in the pictures? Not sure if it's a certain piece of UPVC that could replace this bit