Quality of newly installed wooden sash widows?

[opps]

The company has accepted accountability and they are replacing the affected windows with new..

Glad to hear.

Replacing the top sash is more of a PITA for them than the bottom one. With both, they need to remove the staff bead (inside of the property), with the upper sash, they will also need to remove the parting bead (the timber between the two sashes).

Sash Windows 101 - Sash Smart

Parts that make up a Sash Window. 1. Top Rail: The top horizontal framing member of a sash. Rebated (SEE GLAZING BAR) on the outside. 2. Box Frame: Sometimes referred to as a ‘jamb’, the main box frame consists of three TIMBER LININGS. 3. Sash Cord: The waxed type is best- it runs over the […]

sashsmart.co.uk

I would be extremely surprised if they could refit the beadings, filling and caulking as required and then touch in the filler and caulk in one visit.

Let us know how you get on. Best of luck.