So we've had success with sleep training (No Cry Sleep Solution)

[TheKitchenWitch]

and ds2 9mo no longer wakes multiple times in the night. Instead, he's sleeping beautifully from beditme (between 6.30 and 7.30 depending on naps etc) until 1.30am, then he wakes up, sleeps for another hour and is then up for 1 to 2 hours until about 3am ish.
He's not hungry, or in pain, or wet nappy etc. I think it's just habit because he's clearly still tired, he's very whingy.
Am I right in thinking I could try Wake to Sleep to try and break the cycle?
And if so, when should I wake him, at 12pm? or just before 1am?
Any advice or thoughts?
TIA