Most of the time the Mirena is put in without anaesthetic. Some doctors use some local on the cervix but some think that hurts more. Occasionally, if there is a reason, like you are having another procedure done or it is difficult due to previous surgery then a private ob will do it under GA. Probably possible in public too but there could be a lengthy wait which kind of defeats the purpose.
Sarah87 an IUD sounds like a good option for you too?