Yeah, I have to agree, I was frustrated to find that it didn't appear in the WA panel, and that it had changed in the menu too.
I installed and uninstalled so many times that I was sure that it was an installation error, however, in the light of the new morning, a brainwave appeared in my head... I know, I'll watch the demo video of it, and so of course it was probably there all the time, just not what I was used to looking for. That's frustrating, but not as frustrating as that memento panel!
Anyway, I now have all the extensions working. Thanks for your help Ray. I know these errors are down to Adobe's .dat file, but the memento panel is still yours!