I would note you will almost certainly cover some content related to or incorporated in a neuroscience course in a medical degree, and you may also be able to spend an intercalated year doing neuroscience. So doing medicine wouldn't necessarily preclude you from pursuing interests related to neuroscience.
Ultimately if your primary goal is to enter the medical profession, you need to do a medical degree, and it is easier as far as admissions go, and cheaper, to do a standard entry course as a school leaver (including after a gap year - or even two or three...) rather than a graduate entry course or a standard entry course as a graduate. I would recommend then that it would be better to try and get into medicine now, rather than later, if that's your aim.