Really depends on the type of engineering you want to go into.
Not taking chemistry rules out.... what chemical engineering. Not really the end of the world.
However if Maths / Further maths are in the same timetable block i.e. your going to do A2 maths in year 12 and A2 FMaths in year 13, it may be worthy looking into chemistry incase things go pearshape come exams - But not the end of the world if you dont