I completely shocked all my of mates in college when I told them, I didn't say anything 'till the end of our first year and absolutely none of them had copped it. I've been told I'm extremely "straight acting", to use a phrase I don't particularly like. The other gay guy in my class was a huge shock to everyone too, including myself. Not only did he not ping the dar, he's the last person I would have ever suspected.
My ma had even less of a clue, but it hasn't been brought up or mentioned since then.
My close mates (all lads), the ones I literally see every single day, always suspected it but it was less to do with my mannerisms and more to do with the fact that I wasn't chasing girls and constantly commenting on every girl we knew, etc, etc (anyone with a lengthy dry spell has faced similar speculation). I've been told if I was in any way "camp" or effeminate that they wouldn't associate with me so I think that says enough about my mannerisms. They're the type of lads that think all gay people are running around with jazz hands and handbags and whatnot.
I think with the amount of people coming out these days, it's starting to show that camp/flaming/effeminate (whatever phrase you wanna use) gay guys are actually the minority.