Been helping my parents with exactly this situation on their old cottage, these narrow cottage windows that the original builder clearly made to fit whatever timber was available at the time. Every installer we called wanted to just replace the whole frame with something standard, which my parents absolutely refused to consider since the original timber is in good condition. Ended up checking out about AMB Glass after our joiner mentioned they manufacture everything in-house from their Uxbridge workshop rather than farming it out, and seeing their heritage range explained properly (12mm sightlines, slim cavities) made it clear they understood period properties. They sent over examples of similar cottage window projects which gave my parents confidence before the meeting. Now they’ve got proper thermal performance without losing any of the original character. If you’re researching before meeting your installer, understanding who actually makes the glass in-house versus who just resells makes all the difference to getting something that fits properly.
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