It sounds like you are pushing things a little bit. Like you want to hit the air waves doing 20 WPM on your first QSO. Don't worry so much about speed, until you have learned all your characters. Once you get all the characters down and get on the air, your confidance will start rising. Speed doesn't necessarily come with operating on the air, but confidance does.
Thank you very much for the advice. What I may do, instead of trying 20/20, is slow down G4FON so that it's 15/15. That way, at least, I will assimilate the "correct" spacing. I'm not sure how long it will be before I get on the air, but right now it looks like "several months," mainly because of time contraints in building the transmitter and also because winter weather could make it harder to put up my first dipole (I'm currently just using a long wire for RX). So, in a way, I have the "luxury" of being able to concentrate on the Morse learning for a while. However I'm sure nothing beats actually being on the air, *especially* when it comes to improving one's Morse *sending* skills.
Copying on the air is completely different, when you throw in QSB, QRM and the very basic equipment I'm using. But it's undeniably a lot of fun! I am beginning to get entire words, at least obvious things like "TEST," "THE," "ALL," "RIG," "NAME" and the various Q-codes.
One argument for *starting* at the "fast" end (20wpm+) is that it makes it essentially impossible to "think" i.e. there is no time to "count" the dots and dashes. And that's important, IMO.
This is not the first time I've tried to "learn Morse"; it's actually something like the fourth time (the first one was 40 years ago). All previous times failed because I ran out of motivation, or time, or both. This time, I'm determined to finish!