Celotex and knauf fire resistant insulation and plasterboard - can anyone help?

[Karcheer]

I've been abandoned by my builder, so finishing the job myself...

I've a carport with a bedroom and bathroom above. I'm putting celotex fr5000 in the ceiling of the carport and plan to put fire resistant plasterboard on that. I've got bathroom pipes that run under and I'm putting celotex around that.
My question is, can I put the plasterboard below the bathroom pipes, which would make a space between the celotex and the plasterboard. Or do they need to be flush to each other and then box in the pipes separately?
I'm wondering if having an air space between the celotex and plasterboard would cause a fire hazard, or at least reduce the fire rating.
Or does it not matter?

Thank you!

The important thing is your plasterboard has to be continuous, the insulation just has to be continuous separately. But your building inspector would have the last word. Sorry to hear you've been let down by your builder. We'd be really stuck if that happened to us as they're doing all the structure and roof!

Thank you. That's annoying he popped by today I forgot to ask him.
It's not too bad as the main structure is in place, I've quite enjoyed doing it all tbh, learnt so much useless information!

Glad you're enjoying it, we gave learnt an unbelievable amount in the 18 months since buying a 1920s house and once the extension is watertight and the structure is in place we'll be learning more about plumbing, electrics and kitchen fitting. So now we know who to ask! Good luck.