So I've been busy making lots of modifications to my views/models/controllers - came to test the app and got a blank screen. Nothing in the application.log file so must be a syntax error somewhere... But which file?
The article Fixing extensions without modifying their code reminded me of another patching technique that I used. My conviction and a hard look on the web had led me to an article Redefine PHP class methods or class giving me a head start to do what I wanted: patching third party code without touching the original to allow easy upgrades.