Today was the long-awaited meeting with the window company. Two of them came, spent a good couple of hours on-site discussing the project and taking notes and measurements. They seem genuinely knowledgeable and passionate about their field - sash windows. But when I discussed timeframes with them, they weren't able to give anything concrete, instead saying they would firm this up by the end of tomorrow.
 
The inter-relationship between the windows, insulation, and the cills is particularly complex on the rear elevation. Speaking of which, I need to finalise and order the replacement cills soon.
 
The joist nearest the front wall in the first floor bathroom was rotten, due to historic water leakage from the bath (note, this is a particular danger in highly-insulated houses!). As this wall is to be internally insulated, I asked the joiner to remove the joist; the floor will be cut back to the depth of the insulation. I think he's done a really great job of this awkward task:
 
 
 
Also note the original WC pan connection in the photo, which is made of lead and goes through the wall at a 45-degree angle to the left; this will have to be replaced, again to minimise the risk of water leakage. The soil pipe outside is still the original cast iron, so this will be a particular challenge for me.