Insulation behind UPVC cladding?

Hi all,

Just after a bit of advice,

I will soon be renovating our utility room which is attached to the house. It's UPVC cladded on the outside with timber frame walls. I'm pretty sure its not currently insulated behind the plasterboard which is currently there as it's freezing cold in the winter.

I'm taking out a door and window and replacing with one smaller window so will be redoing alot of the timber work on the front.

The question I have is, which type of insulation is best for using behind UPVC cladding? Do I need a membrane between either the UPVC or the insulation and plasterboard?

I'm pretty handy but not really done a huge amount of construction before so wasn't sure of the best wall construction methods....

Any input gratefully received.