I'm not positive about this because I wasn't paying for any of it, just made the timber frames, put the roof on, pavathermed the outside fitted internal vapour, sealed that up with Tescon tape, covered the Pavatherm with Tyvek, battoned it then clad it.
It would be fair to say that me and another bloke basically did the lot apart from the insulation that went between the studs (which was also made by Pavatex).
We had nothing to do with the costings although the total extension was something like £160 000.
Plenty people took a cut of that money though and I bet some of the people who did a lot less than me got a bigger cut than I did.
The architect was even a decent bloke and it's not often I say that.
If my memory serves me right though, each panel was something like 35 quid, plus fixings.
They were 580 x 1580 or so mm? By 100mm thick.
Windows required a bit of thought and pretty much every cut I did was with a Festool HKC55 set to maximum depth then cut again from the other side to get that 100mm depth.
Oh and if the boards got wet it clogged the saws bladeguard up and needed clearing so the saw was safe again.
Don't even bother trying to cut it with a handsaw, it just clogs the teeth up and stops cutting.
This site gives some decent info about what you need fixings wise although that page is just talking about panels that are different sizes. I assume thats cos the thicker panels get heavier so arent made as big in the other dimensions.
https://lifepanels.com/products/pavatex-pavatherm-combi-panels?
variant=8742784041023