Several months ago, SWMBO's panda was T-boned (NS) and repaired by insurance. Recently, she decided to open the windows to take advantage of the spell of warm weather. As she wound up the NS window, the scraper gasket/moulding was pushed out of place. I've pushed it back a few times but cannot get it to stay whilst the window closes.
I presume this 'gasket' simply locks itself into place?
But how is it now 'not holding'?
Is there some little trick to installation that I am missing?

I don't think it's quite that simple .They probably have retaining clips etc .You will have to explore further but be careful to avoid further snapping of delicate parts .

I've had a look on eper and there is no mention of clips, nor are any shown.