Dunno if this would work for you, Tutter, as I assume ds2 is in a cot.
Ds (2) wakes every day at 4.45am or thereabouts. For the past 3 mornings we have just taken him by the hand, without speaking, led him to his bed and tucked him in saying "sleepy time" which is what we say at bedtime.
1st night back to sleep for 20 mins, up again, back to sleep for 20 more mins, up again, back to sleep til 6am which is the time we've decided is morning. 2nd night up at 4.45 then again at 5.30 then 6.10. Last night up at 4.45 and not again til 6.15!
Hoping that he'll eventually stop waking at 4.45 but until then it's fab that's he's going straight back to sleep with no fuss.