Welcome TheWorstWitch, I hope just posting here helps you realise you're not on your own, which I think is half the battle.
what a shame you've got such heavy periods, mine are pretty horrendous but don't sound as bad as yours. I had a 20 something day period recently and it just drains the life out of you, doesn't it? I've had 10 day periods for the past 2 and a half years and I know what you mean about the horror of a commute, mine is 1 hour 15 minutes and sometimes when someone catches me on the way in I want to scream as I know I'm running out of time! I can also empathise with putting your life on hold, it is rubbish but as I keep telling myself, it won't last forever.
Anyway, maybe the scan will find you have fibroids to explain the heavy bleed? If I had been more sensible, I probably would've got a Mirena fitted 2 years ago, but for various reasons haven't. I have friends who swear by it and have had no periods for years. Alternatively you could get transexamic acid to stem the flow? Options for me are waiting for them to shrink or hysterectomy, so I'm going with the wait and see option.
NHS seem happy with ferritin levels of over 15 but it seems you should be closer to 50-70 for optimal health. Mine was 10 when I was tested (had dropped 10 points in 6 months) and have steadily built it up to 50 something now. I take ferrous fumerate, don't think Floridix would've helped because my levels were so low. Worth getting that tested, as well as Vitamin D (might be cause of muscle pain) and thyroid too. I know you said you were phobic about needles though, so maybe that isn't an option for you.
As for worries about flooding at your friends, I now use a towel, a Boots maternity pad, and sometimes when things are pretty bad, Tena ladies' pants
Have you had any hot flushes/night sweats yet? Probably if you post any random symptom you've had into the search screen, you'll find someone who has had the same thing!
Sorry for the long post, please keep posting though.