All modern houses have double glazing as it is a popular and relatively easy method of reducing energy loss through windows. In terms of payback, other insulation methods are more appealing, but when windows need replacing anyway, installing sealed unit double glazing is a good idea.
Modern glass technologies can offer extra savings, limiting heat loss through the glass, and limiting heat gain in the summer. Argon filling can reduce heat loss through the gap between panes, further improving performance.
Listed building owners will be more limited in what they can do, but secondary glazing is often permitted, leaving the original windows untouched, and installing a double glazed panel inside.
You will also notice a marked reduction external noise getting into your house.