Tbh, I don't think A Levels matter as much once you have a degree coz having a degree is the thing that stands out on your CV, however I was looking in an Undergraduate employers book the other day, and some employers ask for a minimum UCAS points requirement, so in terms of summer internships, may be important but future careers, as long as you do alright at uni, I think you'll be fine.
Don't worry about your first exam btw, I remember my first A2 exam went bad, and it was in Chemistry which is what I'm doing at uni.
Good luck for your future exams though