I think you are allowed one external unit under permitted development, any more and you need planning. Ad-hoc installations of one per flat on a block is really ugly and likely to run into issues. It really needs a big system installing on the roof or something but then it's big works, freeholder run etc. Basically a nightmare.
I think you are allowed one external unit under permitted development, any more and you need planning. Ad-hoc installations of one per flat on a block is really ugly and likely to run into issues. It really needs a big system installing on the roof or something but then it's big works, freeholder run etc. Basically a nightmare.