well here's my most accurate opinion (just finished year 12)...
i do physics, chemistry and biology, so i obv needed a subject to relax and it was french :P
what you said about doing well if you put effort and do well is 100% true because at the start of year 11 i was getting Cs but i kept learning vocab and within 3 weeks (not exaggerating) i was a solid a*...
over holidays all i done was learn vocab and verbs etc >
www.verb2verbe.com ...or verbe2verb dunno
it really put me at ease for year 12 french...and you get used to the level, i done aqa and tbh the jump really isn't that big, and you notice how easy it gets near the end of the year when you do practice papers...even my teacher was annoyed at the difficulty...he said the tape might as well say 'question un, la réponse est B' and the real exam pft that was a joke it's one subject i'm 100% sure i have an a in...
the only thing i wasn't happy about at the start of the year was the fact we have to do written essays in the exam (for gcse it was just coursework for writing), and for that it's important you brush up on grammar in holidays...
and even if you aren't used to writing...you'll get better without noticing...i was actually at the bottom of the class for writing, my teacher was very worried and had to pull me out of lesson for a talk (i was getting something awful like 12/13 out of 35...my last mock result was 31/35, one of the highest if not the highest in the class...
a girl in year 13 got a c d d, guess what the a was in? FRENCH :P
if you do aqa you're very lucky though other boards are probs of similar difficulty...
anyone can do french see if they're really up to it
but if you really don't have much interest in french don't it because then you'll always be in trouble no matter how easy it can get