Thanks,
@Bikes4two, I'll be sure to observe those guidelines.
@saneagle, I'm not going to get into a snarling match with you - however there is a context that is relevant - directly after my observation about my practical skills, I was clear to say "
many areas where my knowledge is zero, electronics and anything that isn't 240v being a prime example." I looked at what you sent, and because of my shortcoming in that area, I could not see anything that I interpreted as something I was going to be able to use.
You ask "How can you explain that it's working now with a good battery and it didn't before?" Here I am at fault for not being rigorous enough in my testing, and not thorough enough in explaining it all.
When I did the battery swap, I swapped the 'good' battery into the 'bad' bike, and the 'bad' battery turned on, I didn’t test it so assumed it was OK. I was making the classic mistake of starting with the solution not the problem (I had decided the controller was at fault and was trying to establish which one). Much later I tried it again and it was dead. I assumed all the battery did was to supply the volts, and that the odd display was the province of the controller. From the start to finish was a number of weeks, with the intense activity only about the time I sought help here. My fault. Sorry.
I know more now.
Again, I’m happy to thank all who have helped, these fora are a great source of information and help, and respect is due to all who have knowledge and are prepared to share it.
Kind regards,
Peter