2 or 3.
Your chances at Cambridge and Birmingham are very low due to your GPA which would convert to an upper 2nd class. That makes you eligible for application but a lot of people have an upper 2nd class, making the competition extremely tough. The other thing is because you are applying as an EU resident? then you will be paying subsidized tuition fees. The reality is, EU candidates need to be better than home candidates for a spot generally. If you are applying international it won't be much easier because again they would prefer a UK candidate although as an international you would be paying higher fees. You have to keep in mind a lot of people apply with a 1st class honours degree along with much stronger ECs than you have. Cambridge and Birmingham both don't require an exam, if you can't prove anything through an exam your GPA and ECs are all they can rely on and at the moment, both are just over the minimum threshold. I could easily find you 100 candidates for GEM who would be able to provide something better to be honest.
There was a candidate from the US who got into a GEM program at Imperial. He had a 1st class honours degree along with a high UKCAT score I believe. That helped his case, however with a upper 2nd you are likely going to need to provide something else to cover for that weakness. If you had multiple publications that would help, but I don't know if you do.
You haven't taken the MCAT yet, and so really you don't know how well you'll do. I really recommend taking it, your chances for a US MD or DO are still alive if you score well. I don't know what your eventual plans are but if you want to practice in the US, no UK degree will be better than a US MD degree.
A 3.5 GPA doesn't sink your ship in the US, but it would in the UK especially since you are applying for GEM programs which are competitive to begin with and you don't have anything else backing you up.
If you've already applied, obviously just wait for the results, but in the meantime, studying for the MCAT is the best option really because your chances are best in the US.