hi - we moved DS when he was about 19 months... but he wasnt so into his cot.
we got a king single with a bed rail and also put lots of padding on the floor around it. he has only fallen out 2 times.
he has slept a lot better in the bed (was a pretty bad sleeper beforehand) as it happens...
we made a big deal out of the bed - took him to 'choose' it, got great linen, brought him in to see it all set up etc etc. it has been v successful here... we get him to show off his bed to gparents etc
hope that helps