I've been asleep, honest! Knowing there would be a solution to my Raspberry Pi automation woes I started to search around 2am.
Google and Stackoverflow.com are pretty handy at this time of night; 'rvm installation not working: "RVM is not a function".
It turns out that all I needed to obviate my need to run the scripts in a login shell was to copy the second line of code from
Thankyou Haris Krajina!
No, I'm not going to wait up.