My ILs have old ass windows that are considered "original" to their Victorian house, so they aren't allowed to replace them.
You'd still have to replace with like windows if it's a "listed" building, so they would still have to be wooden framed, single glazed.
{rant}
Which is, of course, stupid.
If the goal of listing the building is to preserve the historic character of the building and the neighborhood - a goal I agree with - then I am certain there is a way to upgrade the windows without ruining the look of the building.
I'm sure, for example, that the windows of Buckingham Palace have been upgraded at least once or twice in the 300 years since its construction, and I'm equally sure that whatever upgrades have been done have not detracted from the building's magnificence.
It's ridiculous to say a listed building must be maintained completely in keeping with the standards of the time in which it was built. If one of the windows is broken, would it be ok to get the single pane of glass from B&Q, or must it be hand-blown by a glass blower working in a market square someplace?
And if it's ok to get the glass from B&Q, what with the decline in the glass blowing industry over the last 250 years or so, why can't you just get two panes of glass? What is it about the second pane of glass that English Heritage hates so much?
{sarcasm}
If, on the other hand, the goal of listing the building is to preserve historically inadequate methods of keeping freezing cold air outside, providing a test bed for future window scientists to use when they want to examine England's inhabitants and their long and storied history of failing to adequately deal with its climate, then I'd submit perhaps not everyone needs to suffer with poor window design to further this goal.
Maybe it'd be enough that just one or two buildings be required to maintain single pane wooden framed windows; a museum of windows, if you will. Then the window scientists could go around to study it during the winter and say, "Goodness, it's cold in here, and the heating bills are exorbitant! Think of all the energy we'd be wasting if we prevented people from upgrading their windows in an aesthetically pleasing manner, allowing them to live in comfort while using energy wisely, and still preserving the look and character of a beautiful building. I'm so glad we live in the UK, where we're constantly on the lookout for innovative ways to solve problems, rather than just living with them because 'that's the way it's always been done'!"
{/rant}{/sarcasm}
I'm paraphrasing, of course.