Loft Insulation

We live in a house built in 1965 and an extension built in 1995.
Am about to get round to insulating the loft part of the original side, am going to get the rolls of fibreglass stuff from B&Q or similar.
Have read somewhere that polystyrene slabs are a fire hazzard, can anyone tell me if this is correct as this is what is in the extension side.
Just need to know so I know if I need to purchase the fibreglass rolls for this side too.
Thanks in advance for your help.

If polystyrene slabs catch fire then they are indeed a genuine hazard, releasing toxic and carcinogenic fumes such as phosgene as well as others. Rockwool is a good fire break and I'd be inclined to replace the polystyrene with this - as thick a layer as is possible.
Cheers John

You will find that wood burns easily too, and there is lots of this in the loft

There is no reason to replace polystyrene loft insulation, just because it is polystyrene. It is not a fire hazard in this context

However, you may want to check that any electrical cables are not in contact with it as the polystyrene can react with the plastic cable sheathing and the cable looses its insualtion sooner

It may also be worth uprading to current standards