Have you tried day sleeps first? Like Dachlostar said, I love the idea of the star charts to encourage... I started Matilda on day sleeps first when she was really zonked & would lay next to her to help her see what she needed to do...

We also did the band aid effect with Matilda at one point because she kept running to her cot & climbing in and out, so we pulled the cot out of her room & apart so there was no other option but to sleep on her new bed.