Well that was what I meant in relation to the Vampires of Venice - they're basically farming the females to use as baby incubators, or that was my reading of it, so I didn't really see it as heterosexual per se.

I might be misremembering but I thought the Doctor, in this incarnation, was being portrayed as basically asexual. I'm sure there was a line to that effect in The Lodger (when he was asked if he wanted to bring home a girl/boyfriend), and possibly another reference in Vampires (in reference to his kiss with Amy). But like I said, I might be wrong.