insulating loft

[bradlado]

i have just increased the insulation in my loft and was wondering if its a good idea to insulate the loft ceiling as well with a rigid or wool insulator and cover with foil backed bubblewrap or similar.
or do i just put the foil/bubblewrap over my new insulation on the loft floor

[buildersmate]

There's no reason to muck up the ceiling because it makes no difference which side the insulation sits on.
Rigid insulation (polyurethane - not polystyrene) is about three times more effective than fibreglass/rockwool at stopping heat transmission through it (for the same thickness of material).