Okay you're interesting in going into Engineering, then you need to think about a few questions:
a) Do I want to go to University to study Engineering and then find a job afterwards or during?
b) If I do want to go to University what level of study am I aiming for? e.g Top-level at Cambridge/ Imperial or Medium-level at a less-prestigious University but easier to get an offer
c) What would I need to get into said University, does it require specific A-levels or just UCAS points?
d) Could I find an engineering firm to allow me to study/work at the same time?
If you need specific A-levels or subjects which you aren't learning right now like Maths or Physics it may be worthwhile to restart Sixth Form at an alternative college to put you in the best position to follow your aspirations or maybe try switching subjects, though since it is late in the year you may not be able to do this easily. Its a tough decision but either way I would recommend at least completing Sixth Form somewhere. Any qualifications > No qualifications.