^Pretty much this, the grades for medicine are around AAA-A*AA and good MEng programs tend to ask for A*AA with a handful asking for AAA, for BEng you would be looking at AAB normally. So you wouldn't necessarily be better off with engineering if your grades weren't up to par for medicine.
To be honest, I'd go straight for nursing if I were in your position, which I kind of was, I just didn't know how good of an option nursing was at the time. If you're good enough to be considering medicine, then you would likely excel in a nursing career. They make good money (better than doctors during early career, and if you're ambitious as a med applicant should be, better than GPs in mid to late career), they're always in demand, you have a lot of career options, and plenty of opportunities to go abroad.