The problem with the condensation is that the ventilation is
inside the room (for the occupants) and doesn't ventilate
as well the space behind the insulation and in front of
the membrane.

Can this be sorted with a few airbricks?

Essentially there is likely to be a humidity gradient through
the wall.

The vapour barrier and insulation will prevent condensation coming from the
inside.

Anyway the arrangement of the membrane should ensure that condensation
on that interface isn't an issue so I will be insulating between the
studs for the dry-lining. Before anyone comments on bridging by the
studs and using over stud insulation, I know, I know but I don't want
to keep bringing the walls in. Anyway U-value for the wall construction
even accounting for the bridging is pretty good (I'm going for ~0.3
although heat-loss calculation was based on 0.6). I'm really not going
to notice this room on the heating bill.

U-values are not the only reason to avoid cold bridging. One of the main
problems is that you will get localised cold lines, which will lead to
condensation where the studs are. The condensation might not be excessive,
but can often lead to obvious staining from moulds. Can you do the final
"plasterboarding" with something like Kingspan K17/K18? This is most
typically done using a 37.5m board (25mm insulation+ 12.5mm plasterboard).
However, thinner boards are available and will make a significant difference
to the cold bridging situation.

Christian.