We've been pretty lucky, broadly, with 18mo DS and his sleep so far. For the last few weeks though, he's wanted to play for 2-3 hours between midnight and 4am. Really unsettled upset crying, will sometimes take milk or calpol but the upshot is seems to decide after 4 or so hours he's done, and cries until we get him out of the cot to play. Eventually he does zonk out, after maybe some tears in the cot when we've run out of patience.
He still naps for 2-3 hours in the day, which we try to focus around the middle of the day so he's in with a chance of going off at 7.30 or so without being too crotchety. Until he sleeps longer I can't see our way to dropping it (some other 18mos I know barely nap now) but until he drops it, can't see him sleeping through again. Any ideas?