suzieb - when you go for the appointment for the hysteroscopy I would write all your concerns and questions down so you can refer to them when you see the consultant. The hysteroscopy is a routine procedure, I believe they usually use some local anaesthetic, and it allows them to see inside your womb and take biopsies if need be. I had one done and apart from a bit of discomfort it was fine. Maybe take a couple of Ibuprofen half an hour before the appointment.
If you are doing OK with the Norithesterone, then continuing with this for a while after having the Mirena fitted may well be the answer to your problems - you could gradually start reducing the Norithesterone dose after 4-8 weeks to see if the the progesterone in the Mirena is doing it's job but you need to check with your consultant about whether you should do this or not. There are good reasons why gynaes like to use the Mirena, particularly when excessive bleeding is a problem, as it often solves problematic bleeding, shrinks polyps and fibroids and allows oestrogen to be added to relieve menopause symptoms without triggering further excessive bleeding.
It sounds as though you are getting good advice. DG x