Hi I moved in to my home a year ago. Since then our main bedroom has been getting loads of condensation, i mean loads of it!! In the window reveal around 2/3rds of it was covered with UPVC. Sick of the cold i pulled them off to reveal this....(pic) Do i used plaster board adhesive, fill it in with plaster boards then plaster over? Will it be strong enough to hold the roller blinds ( really heavy)? Any thoughts are welcome. Cheers