Door window... open, stuck in a complicated way.

[Oldman]

Success ... partially ... or maybe one step forward one step back.

Putting the glass into the lifter reveals the cause of the problem.
The glass is very very stiff in the window - when the winder is wound down, the glass stays up. It goes down with a push, but obviously has missed the channel at some point, then I've unadvisedly jiggled the winder about, until it's forced itself above the glass and got stuck.

So this thread becomes a new question... why is my window so sticky (presumably something is out of alignment, but it is in the guides either side) and what can I do about it?

Check the condition of the vertical guide channel felts.....they should be felt lined rubber sections.
(These guide channels extend below the window opening as well)
If the felt has worn through.....often happens, the glass will not slide easily against straight rubber (without the felt)

Secondly, the glass lift channel should have a rubber sleeve that locks the window into the metal lift channel section.....without it, you'll lose the glass every time when it sticks.

Thirdly, if the cable/ coiled section inside the window actuator mechanism arm is rusty, it'll be hard to wind up....down is not usually an issue.
If this is a symptom, forget about lubing it.....just replace the mechanism.
All these parts are readily available