Insulation/vapour barrier?

[3Bowls]

Hi all, roof is on our porch and have installed polystyrene insulation from Wickes in between the rafters, with some space for wiring as it shouldn't touch the wires and 40mm from roofing felt and barrier. Was wondering if there should be a barrier between the plasterboard and insulation? Can it just be stapled? The insulation is not foil backed.

Any help would be very welcome.

Thanks

 

[Alastairreid]

Yes vcl stapled between plasterboard and insulation.

 

[3Bowls]

Assume a dpm would be as good. If it was missed would it all end badly?