Gap year after Year 14??

I had to stay in Sixth form for an extra year due to me failing an A-level in Year 12, and taking another one up from Year 13-14. I've already sent my UCAS application off, but i'm considering deferring another year and doing gap-year stuff.

I feel like I want to experience more, and do some volunteering/travelling/work experience ready to start Uni with a fresh head.

I was just looking for advice really - is it too late to do a gap year if i'm already in an extra year at school?