Thank you for this Alex. It explains everything I didn't understand. You have been a great help.
One thing that worries me throughout many of the threads - and it's not a criticism of the contributors, it's loosely based on "That's how I understand it, but to be sure you'd need to run it past the AAA man".
One of the reasons so many of my rides were struck-off the AAA list, was they didn't have enough climbing - fair enough. But that was because the system has never really been explained to me.
I fully realise that all work done by AUK officers, organisers and helpers is voluntary. But If someone volunteers to do something, I don't think it's unreasonable that they make a convincing job of their set task. The AAA system is still a bit of a black art and when reached, the final set-up still seems far from satisfactory.
From what I can make of it, the AAA system is no better now than when it was changed a couple of years ago. There have been no realistic improvements.
Gets off soapbox
PS 4000m is the threshold for a 300km ride, according to the AUK AAA site.