The windows were literally, as well as figuratively, one of the most painful parts of the renovation.
Over time they had lost all of their dust seals (the rubber around the external edges of the frames). Three window panes were cracked. Others had lost their rubber seals at some point as well and had been siliconed in place.
Every window had to be completely pulled apart and refurbished. The silicone used instead of proper seals was not neutral cure. It was literally eating away at the aluminium frame. Not only that, it blocked the drain holes in the frames.
As a start, I pulled all the frames apart and removed the glass. Broken glass was thrown away. Unfortunately several of the intact panes were the ones siliconed into the frames, so I had to break those out and clean out the silicone.
I was able to order and replace the missing dust seals and glazing wedge from the excellent Vintage Caravan Spares online (who also supplied the replacement external towing lights).
Google turned up a local mobile glazier who replaced 6 of the window panes at a bargain price on site, and I reassembled them. The glazing wedge was straightforward and easy to fit.
The dust seal less so – requiring a combination of technique and brute strength.
Then I turned my attention to the openers and catches. These were all original, but showing rust.
I used a wire wheel on my drill to take them back to bare metal, and then sprayed them matt grey to match the wallpaper on the ceiling and walls.