I have a Bryn. One 'n' is the traditional spelling. I'd never even heard of Gavin and Stacy until DS was about three weeks old
It's been mentioned a few times, I won't lie, but not a big deal. Am yet to meet another Bryn, and DS loves his name. He has been called "Brian" on a few occasions, by people just reading his name rather than hearing it - but that's the cost of 'cre8ive' spellings being popular 
Fantastic name - I might be slightly biased but it's fab.