I had the same perscription as RTKangaMummy for a while and it really helped. I can't take the pill or anything hormonal and these were the only thing that helped. Reduced 10 day periods to four days and a lot less clotting too.
I'd be nervous about the Mirena coil if I were you. Actually all your options sound a bit crap - ask for a second opinion. I found out after five years of being fobbed off I had a rare blood disorder - and they couldn't treat it but it was causing massive hormonal peaks which made my periods v heavy.
BTW my problem resolved itself with weight loss and cutting out all sugar/processed food from my diet.