Morning Teaky,
Thankyou for the information given above. I haven't read the relevant documents as I have relied on both my builder (wife's cousin, who I do trust) and the BCI to ensure that everything is done correctly. I will have a read with regards to the fire door regs.
I have fitted 150mm Kingspan between the rafters which as you say is a very messy job. I am also fitting 25mm of Kingspan in the room between the plywood walls and the plaster board.
This was a suggestion by the BCI not a requirement.
Pete