Uni vs. ATC is a tough on and already discussed on these forums. I was going to go for ATC, but ended up going to Uni. I applied for NATS at the end of Uni but instead have had a career from my degree for the past nearly 8 years. I still had the niggling about ATC in my mind though and so am now going for it again. I feel that I'm older and wiser, more responsible and more ready for it in my own mind, but people vary!
My advice would be to visit some Unis and see how you feel really. Perhaps try and visit the college with your parents too. In a way taking the decision to go for NATS straight away is probably more grown up than going off and having 3 years at Uni first!