Has anyone had windows retrofit?

[SupermarketMum]

We have big old draughty wooden single glazed sash windows. They’re in surprisingly good condition.

we had a company quote for retrofitting them with double glazing and draught- proofing the frames. Apparently it’s 50% cheaper than fully replacing the windows.

has anyone had this done, and has it actually improved the energy efficiency of your home?

We did it with ours and it made a huge difference. Just about to install secondary plastic glazing too but that it just to try to reduce our bills a bit. We have replaced some windows with new ones and they are just not the same quality as the originals. I will we had refurbished all of them.