Well, at last I've done the fiddly bits on the last sash window,and so the job is effectively finished and I can now post a few photos. Firstly, here's what it looked like before we bought the place (first seen in August 2010).
Then, here's what it was like after removal of the ivy (and we moved in - July 2011):
Here's what it was like after a quick coat of paint on the (concrete) cill and the fake stucco (probably later in 2011, or else in 2012):
Finally, here's the finished product (2018):
As you can guess, I am pretty pleased with the result, especially as the old wavy glass can really be appreciated when it catches the reflections and, of course, the fact that both windows work as intended!!
I am now certainly qualified to give advice on refurbishment of Victirian sash windows, having started with absolutely zero knowledge.
Edited 25 Aug 2018: I just found that I made a miscalculation. I added a nice brass latch and a solid brass handle to each of the windows, and then found that one of them wouldn't stay in place as it did before. Clearly my weighing to make my lead weight was too accurate as it didn't take account of the brass handle, which has now been removed. Drat!