i did the exact same subjects to you in year 11, except that instead of legal i did modern and for year 11 english was the only subject i was actually excelling at, but then i pulled through and ended up with comfortable marks for all my subjects. there’s no need to drop down to save your other grades - your other grades are more than fine. i don’t want to sound patronising but 78% is not bad for english advanced in year 11, and that indicates you have a decent foundation of english skills, all you have to do is try to focus on the individual aspects of english that are barring you from the higher marks; i had a lot of friends who averaged marks in the 70s in prelims but then locked in for year 12 english advanced and all ended up with comfortable band 6s. are you averaging around 70s across all the different english assignments (creatives, essays, short answer, etc)? or is it one particular skill / type of assignment that pulled you down? try to ask those questions as part of self-reflection and then move forward into year 12 english advanced bearing them in mind. make sure to get a lot of feedback from a teacher or tutor and to draft and to look at exemplars etc etc moving into year 12.