Full fill cavity wall with PIR

[Deep86]

I'm going to be getting major refurbishment done at my house that hasn't been touched for 40 years or so. I'll be removing a few external walls and extending them out, but in doing so the solid wall will become cavity walls.

I assume I can't leave the cavity completely empty? So if that's the case can I use these https://www.insulationexpress.co.uk/cw4000-cavity-wall-insulation-board inside the gap?

I've also seen this brand:
https://www.ecotherm.co.uk/products/eco-cavity-full-fill

I have read that if my cavity is 100mm wide I should use 90mm thickness insulation, this stops the possibility of water coming through the bricks into the plaster inside

1. Are these what I should be looking for?
   
2. Is full fill better than partial fill?
3. Are there better options or things I need to keep in mind?

Sorry if these are basic questions but this is all new to me

Cheers for the help!

 

[stuart45]

The 10mm gap is more about giving some room to lay the bricks. It wouldn't be practical to lay them tight to the boards.
The gap will be partially filled with some mortar.
If you look at the ends of the boards you can see the way they slot together stops the moisture getting through.