If the buildings were new, there is very often a planning condition which says that the glass must be frosted. If they breach that, would be a matter for the planning department at the local authority.
Whether they can open the windows or not would depend on who owns the land over which the windows are opening and how often they had been opened the last 20 years because even if they are opening over someone else’s land, after 20 years they acquire the right, by prescription, for the easement open the windows.
However even if that were the case and they had not been opening the windows to 20 years perhaps because they had only just started installing open windows, if the open windows open over someone else’s land, and not your land, it would be for the landowner, not you to take action.
There is no common law right to privacy in English law. People very often get the right to privacy mixed up to the Human Rights right to a private and family life which is different.
Unfortunately, if the neighbours replace the glass with ordinary glass and start opening the windows, then except as I have stated above, there is probably very little, if anything you can do.
Can I clarify anything for you?
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