Hi honorsmum
I can understand your feelings - I was offered one a couple of years ago when I had a hysteroscopy - it would have been very easy for the gynae to pop it in at the same time. I refused but my reasons different from yours. I'm not bothered about having a physical thing up there, but I was worried about the systemic absorption of the synthetic progestogen, levonorgestrel.
The advantage for women in peri-menopause is the continuous progestogen which regulates the bleeding. Tou wouldn;t want to use utrogestan vaginally all the time ofr obvious reasons (

) and using it for half the month will not regulate heavy bleeding in the same way - in fact at your stage bleeding could be even heavier until your ovaries begin to decline, due to the added oestrogen.
The other alternative is a non-licensed progesterone which doesn't tend to be used now - Cyclogest - which are waxy capsules used as pessaries or suppositories (the latter not to everyone's taste

). I used these for several years before the advent of Utrogestan and was prescribed these by my GP. With a suppository there is systemic absorption but not the digestive issues although interesting effect the next morning

!!
No need to work yourself up about it and cause yourself extra stress, if you are not happy with the idea of a Mirena - and why not wait a while and see how you feel generally? In the end you may find the decision is made for you in that you decide you are prepared to try something to enable you to feel better?
Try not to worry...
Hurdity x