me thinks that methods aim indicates a pretty high degree of confidence...
Seriously though, I'm in a pretty similar situation (though I couldn't be bothered with any extension courses...) where physics will likely be my seventh subject. I haven't learned the concepts properly; I get pretty average marks on the tests. I'm just hoping sometime in the next four months or so I find the motivation to start comprehending the actual ideas behind the physics course.
Given that you say that you enjoy physics, at least consider looking over it during the holidays (i.e. read through the study design, etc) and make a decision after that. You might well find that, with the added knowledge gained from spesh and UMEP maths, applying your knowledge gets easier.