he only way how we fixed the early waking was excessive cot-playing during the day and we really attached him to his lovey. We started this as Tracy said: put him in the cot during the day for a minute or, bring new toys and then leave for a few seconds, then minutes. Now he plays in his cot for up to an hour reading books.
After that he felt more comfortable in his cot. When he then still woke at 5 we went in, put him down and said night night, it's the middle of the night and then I went back to bed. He protested for about a minute, then went back to sleep and when he wakes up (6ish) he plays quietly in his cot with his lovey Kasimir. It's great! Teething and seperation anxiety also made the problem much worse.