Thanks for all the help everyone - and for that other recipe, which I saw a little late! It uses much less juice even taking into consideration the one fewer egg yolk...sounds lovely! Might try that next time.
The good news is that I had far greater success on the second attempt! I made a few changes - my eggs were too cold first time around, so I made sure they were room temperature second time; I whisked them for longer second time; I used less juice (about 270ml) and I cooked it for the time specified (35 mins) even though it still looked liquid at the end, rather than 'centre barely jiggling'.
I'm not sure it's perfect - but it tastes yum and I guess that's all that matters :-)
Thanks again to the helpful community.