Hi Engin
It's looking good. I would suggest a small lip to the front of the nest boxes so that all of the bedding doesn't get scratched out and the dirty bedding doesn't get pushed in, also do the same with the entrance again so that they don't scratch all their bedding out. For exterior materials tongue and groove looks nicer but 12mm exterior ply is a better material with regards to harbouring red mite as it has less joints for mite to hide in, of course because it doesn't look great then that might be a compromise too far for you which I can understand. I forgot to say that the grill to the front is a little bit big I would cover the bottom half of it or it will let too much draft in when there is one at the back as well, the idea is to let plenty of air in but not create a through draft anywhere near level the birds are roosting. I would also use a smaller grade of mesh, you would be surprised how small a gap a weasel can squeeze through. Hope this doesn't sound critical because it's certainly not meant to be, it's just nice to give people the chance to not make the mistakes you've made yourself.