Regardless of how much it costs, if it's your dream course, then you won't let money hold you back, (unless you can't get any fee loan thingos). If you do Biomed/Eng, after your 5 years you can either work as an engineer or get into postgrad medicine.
If you do just Biomed at UoM, then the only eng option you have is Biomedical Engineering. I would pick the first option. After a few years, you'll probably know if you'd rather do Medicine or Engineering and thus can drop either part of the degree to focus on the other. At UoM, you'd be stuck into biomed unless you transfer over to science. Also the double degree will allow you to experience Biomed and Engineering in more depth than UoM's degree which in my opinion is a much better thing to do