I actually have a baby gate across DS' door. It took about 2 nights until he realised he wasn't able to get out and he's been fantastic ever since. Once I put him to bed (most nights) he just stays in bed until he wakes at 8.30am the next morning. He doesn't generally wake during the night at all and we never hear a peep.

There are the odd nights here and there, but 95% of the time he is great.
He has the same bedtime every night - 7.30pm.

We are going to start trying to take the baby gate away in coming weeks.