I am currently going through the process of applying to GEM and, having achieved a 2:1 in medical science from Birmingham, and getting a GAMSAT score of 64 and 2 interviews, I did not get a place this year. I am going to try again in October but am also struggling to find a job that shows my commitment to medicine whilst also allowing me to earn enough money to get by as well as save the £3,500 required for first year.
My advice is, do all you can to get into undergrad - you only get one degree with full funding - give it at least another shot with a gap year before thinking of going the GEM route. The way things are going, I'm pretty sure fewer and fewer universities will be offering the part-funded 4 year route (Leicester are no longer offering it for 2016 entry), and even if you do get in, the idea of £60,000 more debt added onto my 17 grand from my undergrad is a constant worry in the back of my head (and that's with me getting in before the fees went up so I hate to think of the debt someone in my situation a year later would have!).