Thanks for all the comments, 
Splint, not really sealed the windows into the brickwork other than fixing with four frame fixings and then a bead of overpaintable frame sealant around the edges on the front,
George and Dark Lightning, the units are argon filled low e glass so hoping that will add a bit of comfort, Kelly, already makes that room seem quieter and Petey, there another 12 to do, 4 of which are nearly done. Thanks also to everyone who commented on the blog.