I was going to get some done with G bits as he can do laser cut thin perspex, but I just havent got around to geting it done. trouble is you just cannot guarantee the exact dimensions of every window as it isn't a plastic model using a solid die as a mold, so you would still have to fettle most of them I think, however you could get the round ones done which would save some time cutting them out. For the rest it is far quicker and easier just to cut them by hand and "Araldite Rapid" them in place, carefully wiping any excess off with a cotton bud dipped in meths as this disolves the Araldite, job done.
looking good there Dave, you need to put it next to another loco to give it some sense of scale!!!
cheers
Rob