It's not a flat as in a block of flats. It's semi detached, one storey over garages. Some neighbours have had them fitted, and the only criteria, I believe, is that they have to look the same as the old ones, due to various covenants that were put in place when the development was built. I will check things out, but I don't think it's going to be this year now.
Be careful buying new windows Simon as they may have to meet a higher specification since you live in a flat. You need to check your lease. Put the wrong ones in and the building may not be insured.
Get that FENSA certification
Oh yes, when it's done it won't be by cowboys. I already have a shortlist, all local established companies. Not a Ted Moult in sight!