cavity wall insulation and plasterboard reveals

[vegman]

I am thinking of having cavity wall insulation done, and on balance it seems a good idea, with little risk of problems given my location, structure of house etc. One thing that does concern me is that the window reveals seem to be just plasterboard across the cavity - there is no brick at right angles to the wall. I think this probably goes back to when double glazing was fitted and the windows may have been enlarged slightly. Anyway, this would mean that the insulation would be packed up behind the plasterboard in the reveals. Is this advisable, or could it cause damp problems?

[acsimpson]

We have a similar thing where a new doorway was put through the old external wall into a garage conversion. The sides of the doorway are just MDF accross the cavity and I wonder if this would potentially cause a problem in the future if the cavity was insulated.