'I only went and fixed it, I only went and fixed it'
I had an hour to tinker with this problem this afternoon and had another go using the 'pull-the-fuse-while-the-window-is-in-motion' routine.
The advice on the link from the US forum is only half the story. In a nutshell, to reset the window park sensors you have to do the pull the fuse routine twice, once when the window is opening and repeat it when it's closing. The window now parks successfully when it finishes opening or closing.
As an aside, I stripped the old unit and there are two (yes, two!) circuit boards in it, one sitting just under the switches and a larger one beneath it, vertically. All very clever but not user maintenance friendly. I'm glad I made the choice to locate a second hand unit, I very much doubt I could have rectified the old one.