Can I just say I wish I had done this earlier!!!
It has made a TREMENDOUS difference to the bedrooms and I couldn't be more happier. It is absolutely fantastic – my son has moved back to the corner room and now sleeps with the blinds open and loves the room now. He had previously moved out because it would get unbearably hot in that room having windows on two sides of the wall.
Thank you so much again – it took long enough for me to do it but so glad it's done now!