John, one of the only two crittal approved companies in my area, the only one who does refurbs.
The top arched sections of those windows look to be what is called "curve on curve" work which in timber joinery is generally regarded as some of the more complex, and therefore, expensive, work to undertake. I agree with Mr. Rusty that if you can't find a shop to do this in metal then a good joinery shop should be able to do an appropriate timber replacement providing they are good enough to do curve on curve work (and I'd insist on seeing an installed sample of this as many shops simply won't have the appropriate experience). But I am also dubious that a double glazing firm could handle the curved DG units for those top sections - I've seen DG units made to curve in a single plane and DG units with an arched top, but never one with an arched top on a radius. Maybe worth asking around DG suppliers to see how feasible that is before considering other repairs or replacements?
I have a suspicion that what they mean is "cannot be refurbished at a price we can sensibly do commercially".
Everything can be refurbished at a price. As
@JobAndKnock identifies these are complex windows. They look great - the thin glazing bars and the architectural form of the windows is excellent. I suspect that the vast majority of companies will only price for a "near enough", which might be just about acceptable (but won't fully reproduce the architectural detail) or will, in fact, look horrendous, changing complex curves for flat panes.
What is actually wrong with them - from the photo they don't look too bad at all. It's not as if a window is some piece of precision engineering like a classic car engine or something like that which needs exotic machinery and skills to repair - a window is a fairly basic construction. I'm sure each panel could be removed, temporarily blocked up and then disassembled, repaired, painted and reassembled. I would be doing everything to keep these because they are definitely worth keeping. In my view windows are critical to the architectural integrity of a building, and so often people replace what was original with some horrible alternative that just looks wrong.
