re: The die is cast

Believe me, the windows are beyond saving. I have previously tried thin consolidating epoxy and filler but I'm not happy with the way that turned out after a few years. There is so much weathered timber in there that I don't have confidence in the paint sticking, even with specialist primers. This is an upgrade project as the windows are single glazed, so they are noisy and not energy efficient, they don't have any draught proofing either. If I did just double glaze and draught proof what's already there, I would still be into a hefty chunk of change. Making new sashes and frames will probably add about another third of the cost of the glass and sundries, based on 6 windows  in progress - glass and draught proofing, new spiral balances etc approx £1200 timber coming in so far at under £400, so for my own peace of mind, renewing is the way to go. Plus it will be a lot easier doing this on a bench rather than in situ.