Has anyone ever replaced steel openers (windows) within timber frames?

[Tatlerer]

Rather specialist request I know! We have original 1920s timber windows and are looking to replace the glass with a double-glazed alternative. The opening sections are edged in steel and we've been given permission (as we're in a conservation area) to replace with aluminium alternatives but even the slimmest profile seems quite chunky and would sit in front of the timber, looking rather odd to my mind!
Has anyone replaced steel casements? Help!

Yes we have similar windows (1925 house). We replaced just the metal units keeping the original outer wooden window frames (if that makes sense). We used Met Therm windows and they were great www.metthermwindows.co.uk.

We previously used a different company fir just a couple of windows (in same geographical area) but were not impressed.

Thank you pericat, this looks like just the thing.