Ooops I forgot one more thing. All 3 previous babies have been posterior, does this prevent you going in to labour on your own?

I've wondered this too. But when my baby was posterior and my OB attempted an induction it didn't work and I just went home the next morning. On the other hand, one of my girlfriends had a posterior Bub and she started labouring before her EDD. I went home after my failed induction and a few days later when we tried again it worked and my baby had turned.

My advice is to talk to the OBs well ahead of time, tell them you really want to give Bub as much time as possible to choose a birthday. If all else fails, you could just 'forget' to turn up to your planned induction. But it'd be better not to. I'd just keep saying 'I feel really uncomfortable with that' to their suggested induction dates until they are prepared to let you go as long as you think is right for you. Or...you could lie about your LMP...

I like Rosehip fairy's advice to take your husband, somehow husbands seem to be taken more seriously.