Paul Jackson complains that the planners prevented him putting in double-glazed replacement windows in a Victorian house in a conservation area. Good! It’s not just the oversize plastic sections, it is also the blue tinted glass and the peculiar hollow in the reflections that make such windows look horridly out of place.
In the general case, there is a simple energy-conserving alternative: a secondary sash fixed inside. It may even be cheaper and more sustainable than having all the existing windows ripped out, and it will provide better sound insulation.