renovating ceilings in flats

[leepylee]

Hi. Ive just bought an old building of five flats and an empty shop next door which will become another two. I am having to drop some ceilings because I have to repair the joists The cielings were double plasterboarded with wool insulation. I want to put them back without involving the council about building regs. can anyone plese tell me what materials i should be using so that it complys for fire, sound heating etc. the house is in south wales . thanks