i would NEVER normally advocate graduate entry but OP i think this is the best route for you. my other half is a final year medic at soton after entering it via the bm6 course. she has said that they received something like 600 applications for 30 places which is insane. this year, for the first time ever in the history of bm6, they have been rejecting masses of candidates without interview which is something they never did before - not even last year. they had a 30% increase in applications this year and next year is only going to get tougher - read the BBC reports on the education section. believe me, i know exactly what it feels like to only want to do medicine - it took me 3 years af applications to get in. only thing is, is at the moment you may think you know what you want but when you get into uni sometimes things change and your feelings for what you think is right will change.
i would advise, if you get AAA then yes take a gap year reapply. If you get below AAA, go for grad entry. you are severly restricting yourself to only applying to these 6 year courses