Thanks Melissa and Sylvia!
Feeling better this evening. Although it took him nearly an hour to fall asleep tonight, he fell asleep with me sitting in a chair about a metre away from the cot, so I AM making progress! and 2 nights in a row he hasn't woken til around 4am, then again around 6.45. That's pretty good!
The question is, will earlier or later bedtime/naptime help??? Trial and error I guess!