The way I see it - you've demonstrated that you CAN apply yourself, your turnaround says ALMOST as much about the establishments as it does about you.
I'd also advise you to stop worrying about things you cannot change. The GCSE's are history - they're gone, nothing you can do about them.
Life isn't like a book where you can tear pages out, pretend they never happened and start over again. What happened in the past is a part of you and it sounds to me like you're able to justify your poor GCSE results. And like they say about boxers - "you're only as good as your last fight" - it's the A level grades that matter.
Stop wasting energy on stuff you can't alter and concentrate on moving forwards.