DS has started sleeping better recently anyway - even before he dropped to one sleep. Half the time he only wakes up once, the other half he wake around 3 times. The main thing with dropping one sleep is that it means he's in bed for around 12 hours a night now, instead of 10-11 like he used to, cause he's going down earlier.

OMG really? So there's hope for me? DD is a lot like your DS wrt sleep. Maybe she will magically get better soon! Waking once would be a dream, LOL.