fire resistant thermal insulation

I need to 'beef up' the insulation I have in my home.

One of the bedroom is built over an unheated garage and has 3 external walls. I'd like to improve the insulation between the garage ceiling and the rooms floor.
I'm looking for an insulation board that can eisily be fixed to the ceiling, but is fire proof or fire retardant.
Can anyone suggest any products.

I've been doing a bit of research since my original post. I could use a new foil type insulation, attached to batterns and plasterboarded over. I have also seen a DIY type injected foam insulation pack. Anyone heard of this? Will it lead to condensation between the floor and ceiling?

One of the easiest I have done in which a average diy'er should be able cope with is use to buy a suspended ceiling kit as they do in offices and you can also put the insulation above the ceiling tiles if needed.
The other way is wall plate on walls with joists hanger then insulation with plasterboards etc.