Belle1,I use bespoke progesterone at a 50mg dose continuously with Oestrogel and it works very well. Unfortunately, if you have bleeding problems, this dose will not work for you because it is way too low.
It's a pity the Mirena coil didn't work out. I wonder if you should try a different patch or gel to get a more stable dose of oestrogen?
I doubt the migraine aura has anything to do with iron deficiency. That said, it might be worth having a blood test to check your levels and at the same time get your oestrogen levels checked because they might be too low and it could be causing the auras.
In the meantime, why not try changing the patch a couple of days earlier, it might help to keep your oestrogen levels stable.