If you're not willing to do Physics at A level, I am afraid you will hate your engineering degree. Being completely honest, engineering is basically maths and physics. Yes, you will be at a disadvantage if you don't do it at A level and you might find yourself struggling for a place at a 'top' uni when you apply (you can immediately discard the very top unis though, as they won't take people who don't do Physics; remember you are competing with people who do Maths, Physics, Chemistry and Further Maths, out of which you only have 2). Not only will you struggle with the FM you haven't done during your first term at uni but with Physics too.
I'm sorry if I sound harsh. People had to be completely honest with me for me to realise what I had to do to do what I want to do (if that makes any sense lol)