Hi @Indy reading some of the replies above and based on my own experience i would agree with the fact that your architect has given you a build spec without any real consideration as to how difficult the wall and roof detail will be to build in the real world.
The floor is a odd thickness, i was told a block is 225mm tall and the 1st row will sit on the B+B floor with a layer of DPM on top so you will need to lay DPM across the floor and up the walls 225mm, so you have 225mm to play with i opted for 175mm insulation and 50mm flow screed, your only adds up to 185 so not sure how that is going to work out on site for you .
The walls with PIR are going to be a nightmare to install correctly personally I wouldn't even entertain the idea, I would even consider if you don't want to increase the size of the cavity going for full fill batts and accepting 0.017 u value done properly rather than 0.015 with PIR done half arsed.
Totally agree with @Iceverge regarding the roof .
IMHO putting PIR in between rafters should be the choice of last resort, fluffy stuff between the rafters and PIR above or below or combination of both .
But most importantly whatever you choose to do make sure that it will be achievable on site in the real world, you would be far better of have a house built to basic building regs but done properly than having a higher spec but a difficult design and ends up being build poorly.