Ah, I didn't realize you are in the UK/EU sort of university? The US isn't that rigid, there's more flexibility, we have four years instead of just three and the first couple years have more general courses and electives but I realize UK universities are more dedicated to a subject so can imagine psychology and only psychology, so help me, etc.

I would base how well I might do with the science/medical stuff by how well I got along with my psychology courses; even the basic ones I had are quite detailed since one has to learn about the senses and how they work in the brain and I know my University had a dog track (Pavlov) and shark tanks, etc., enough science to see if you can improve on how well you use to do because you're more interested or something? I always did poorly in science, never had physics but with my second degree I decided to take astronomy, since it had some physics and that sort of problems in it and I did fine once I was older and more interested in studying for the learning/my own sake than just because I "had" to.