Active job

Ceiling insulation & false ceiling install

Looking to insulate and install a new ceiling in a room above our garage. Currently there is the roof and then lining, and some old ceiling tiles but it isn't very warm in winter and gets too hot in summer. Looking for a layer of insulation - either traditional or polystyrene. Then looking to put in a false ceiling, either wood board or gib. Would rather the ceiling was within the existing beams rather then secured on the bottom of the beams to maintain the height of the room. Also looking as an optional job to install some insulation under the floor which is the roof of the garage. Open to advice and suggestions on the workplan.