I hate to say it but BC have accepted a scribble on a piece of rough paper stating that an Armstrong suspended ceiling has been selected and installed according to manufacturers instructions. The ceiling is in a large commercial kitchen below a bedroom floor in a hotel. It was required to have 60min resistance. Having had a good look at it, I am not convinced at all. Neither I nor BC were provided with specification details so I have really no way of making an informed determination. What bewilders me is that BC don’t seem to have learned anything from the tragedy of Grenfell. Are they nothing more than gatherers of certificates or is this LABC officer just a poor example. He even missed an new emergency final exit that was stuck shut!

anyway, I am looking for a spec for a 60min Armstrong tile fitted below a timber joist floor. 

It's a perfect (& common) example as to why the Building Control process is rotten. If it's OK on the proposals & draft plans it'll do them. They will claim they don't have the time to do a proper snagging exercise nor is it their problem. That's why some completion certificates have small print disclaimers.