I had an anterior placenta with both Charlie and Lexie........and gave birth vaginally without any issues or pain relief after trouble free pregnancies........

A friend told me that unless it moves in the next 20 weeks (which I guess is quite likely) that I would likely have to have a caesar?
This is incorrect. I think your friend has got muddled with placenta previa.

As far as I am aware, anterior or posteria placenta is just a phrase to describe where the placenta is sitting: it'll make no odds either way. Nothing at all to worry about.