Okay I have now fitted this new module and it works as intended!
Just a couple of points for anyone that is a bit cautious about fitting things into their cars, I tried to remove the switch by using (cheap) plastic tools from a "mobile phone repair kit" - that was a very bad idea as in the Northern UK ambient temperatures, the car's plastic is quite hard and I broke the end off my plastic tool I used, so I reverted to using stronger plastic tools from my "car trim removal kit" and that worked very well. After fitting the module, I checked its operation and starting from after fitting this module, mirrors unfolded, mirror switch in "0" position, I switched on the ignition > mirrors partially folded and then unfolded, ignition off > mirrors did not fold. So, with the ignition off, I locked the car, then unlocked it, switched ignition on - unfolded mirrors did not move this time (good), switched the ignition off - mirrors folded. So don't panic if this module does not operate as you had expected initially, it will do maybe after locking and unlocking the car - or maybe, if I had folded the mirrors before fitting this module it would have worked immediately, I'd guess that this controller's logic needs to get into the correct initial state - that is all.
Well now that daughter has just been given her birthday present, though I might add an early oil change to avoid doing that job in December when the temperature will be a lot lower!!
Edit:- I'm not sure that I know how this mod will affect the spiders that are living in these mirrors though, I've blasted them with freezer spray a few times but days later new webs appear!
Another Edit:- now that I've read the "Controller Logic" notes on the installation
guide, I'd reckon that step "3" covers the reason why this mod did not work from first ignition on. Normally I do read all instructions before I do anything as I'm a retired test engineer - but this time well ---- !!!