ask if you can change classes; if not then ask yourself, will you be happy learning english with this new teacher, if the answer's no then change english to sumin u like else, if the answer's yes then stick with it, either way asses the new teacher and make a firm decision, gl
Obviously this teacher means alot to you and is of great inspiration to you. But you also got to remember that the 'best' he brought out of you wasn't his doing, it was yours. Even if you in another class, just work as hard as you would if you were in his class. You can still ask for his advice outside of class and if your worried about the other teacher being bad then there are plently of resources on here that can help you with your A levels.