Have you tried keeping him awake as much as possible during the day? It might help him to be more tired at night... Another thing that might help him, is making a clear difference between day and night - close the curtains after a certain time and keep the lighting and sound low, try to keep him out of his bedroom during the day so that he recognises that that is where he sleeps and not plays... Try introducing a bedtime routine as well - something like telly goes off, bath, pjs on, up to bed, story, lights out, sleep.

I really hope something works and he settles down soon,
