I need to provide a 60 min fire protection between my public house and living accomodation above.

The floor between consists of 225 x 60 timber floor joists at 400 mm centers, timber tongue and groove floor boards, Lath and plaster ceiling which has at some time had timber battons  and 12.5 plasterboard fixed to it .

I proposed to overboard the ceiling with 12mm fireline board , coverstrips to joins and emulsion the fire board. ( would this give me 60 min protection ?? )

You need to seek British Gypsum guidance (White Book) check out http://www.british-gypsum.com/products/gyproc-fireline?tab0=2. What yo are trying to do, is make do and mend, the only way to get a definitive answer, is to rip off the old and replace it with a new, BG will provide the guidance. 

Have you spoken to Building Control?