You need to travel for Chemistry, because over 20% of your AS, 10% of your GCSE, is practical, regardless of board. You'll also need to spend £400 - £900 to do it, unless you have it all down already and just want to get it all done at a school for one day.
I probably can only comment after I know what grade I have, but it seems with Chemistry it either clicks or it doesn't. It's pretty inane in that it's more about remembering all the little facts, of which there are hundreds, moreso than other subjects. For example, you may be asked what creates a certain colour when reacting with a certain something else; there's no way of working it out, you either remember the answer or you don't, and the marks are stingy because of this lack of method.
In hindsight, I might've chosen a different subject, but who knows maybe I'll get a B.
Apparently Biology is tough, maybe tougher. So of the 3 it might be Physics that's easiest. I might just not be remember, but at least in the learning there's no BS with Physics. It's part Maths, part learning about the world. The exams and mark schemes are probably BS though, right?
Also, you see your GCSE grades?
*Throws them into a fire*
YOUR GCSES AIN'T NOTHIN'. DO YOU THINK THIS IS A MOTHER****ING GAME?
Edit: Never mind, someone bumped this old thread. I'll leave the answer for anyone else who has the same question.