Ok, so no real news either way; it didn't go as well as I'd hoped it might. But I do sort of have some info that at least could be usefull for the ongoing saga.
Firstly, they did essentially try to follow H440 (hopefully they would have done that without my pushing it) but according to the technician who I did get to speak to, updating the TCU does take around an hour - and only at the end of that do they find out wether the update actually worked. Mine didn't, which I think has been reported before on here. He had updated the IGM, but without the TCU updated, he didn't even bother trying to do the updates to the Info Module and another one I can't remember at the moment. Important thing to note is that the time the car is in doing stuff is a lot longer than the time you should be charged for - I was only charged half an hour, even though I was there almost 2 hours in total.
Secondly, they believe that what happens is not as I thought - the "turning off" of the SOTA was not stopping the car asking for updates, but setting the JLR servers to either ignore the request, or say there are no updates. This should have been done based on the VIN - the "certain JLR cars" being the range of VINS identified as potentially not being able to update succesfully, and this would have been the same range of VINS that would have had the H440 campaign appear on the TOPIX screen that we all know and love - obvs mine wasn't part of that VIN range, so updating the modules purely because there are updates available is our way of seeing if those updates trigger the servers into allowing SOTA again. This does feel like their initial "range of VINS" was inaccurate, and explains a lot in my mind. There are some further conclusions about JLRs accountability that I'll ignore for the moment.
So the story continues - to be rebooked in when I can next get it there - maybe with a courtesy car next time - the technicians apparently "clock in/out" when they're actually working on the car - so charging for other time shouldn;t happen.