Surnames are bugger! Also expecting our first daughter any day waves at OP and we had a bit of a set-to over surnames. We are not married and never will be, because I don't believe in marriage. I'm not ideological about baby having my surname - I'd like us both to be in there in some way. Buuuuut...
He is a double-barrel, because when his parents married his mother was the last of her line and wanted to keep her name, so she had her husband double barrel with hers - Hername-Hisname. So we can't really double barrel his and mine. I thought we could double-barrel mine and his mothers, or to do a combo name. But he was a bit anti; HIS brilliant idea was for us to call first child one of our names (mine or his, he doesn't mind) and then second one the other (we plan on two). I said this was stupid, as (a) we may not be able to have another and (b) the kids would then have different names to each other, which I think would be a lot weirder at school than them having different names to either him or me. He thinks it's a bit unfair for me to insist on using a single name for both and it being mine, since it's down to me we won't be getting married... sigh
Long story short we're probably going with his name, just because it's bloody easier and he's more bothered about it than I am (his family set more store by this sort of thing, mine is more of a mix and match divorce-ridden hodgepodge so we've got about 5 surnames rolling around in there, and have never felt less like family because of that). Not ideal, and I feel a bit like the sisterhood would disapprove; but certainly if I ever get any indication from those in authority (schools, registries, passport control etc) that I am any less my child's mother because we don't share a surname will catch the rough end of my tongue and no mistake. We're not living in the dark ages,families take man forms these days and they should simply accept that the person presenting as the child's mother is her bloody mother, whatever the surnames.
But it does bother me how many people on here seem to think not getting married, or not taking your partner's name, means you're less committed to each other! This is simply not true in our case. I don't believe in marriage because almost all the marriages in my immediate family I've seen either ended in divorce or are deeply unhappy, where as all the successful relationships have been long term cohabitations. Newsflash: marriage does not give you any kind of indemnity against relationship breakdown. Nothing will but you, and your other half, working at it, every day. Now I loves good wedding, don't get me wrong, but the idea that standing up and making a promise in front of people is some sort of talisman against breakup is nothing more than a comforting fantasy.