I've just been on the phone to Building Control (BC) asking if UPVC
door and window frames need cavity closures, using either:

the propriatary strips (e.g
http://www.screwfix.com/app/sfd/sea/...pi=1&cn=1&cd=1)

or a run of dpc up the edge of the outer leaf of the cavity wall and
then folded back into the cavity.

I was told that it is best to do this as there is a small chance of
leakage to the inside edge of the frame which could then pass onto the
material used to cover the reveal (e.g. plasterboard)

Another point BC made was how was the plasterboard to be supported on
the outer leaf. If a small lip was left (i.e. the frame was not flush
with the inner edge of the outer leaf) to fix the p/b to, this is then
a cold bridge and there is then the risk of black mold growing up the
inside edge of the frame.

Questions.
I would like to use dpc and not cavity closures if possible, so is
there a method of supporting the plasterboard in the reveal?

Is the risk of black mold growth high?

Thank you