I can see that the nightclub timescale would be wrong for you - it's wrong for most people, unless it's a club you go to regularly where you've seen the person round before and are in a kind of familiar social space.

I was having a think and reading all these replies and I see the point about the defensive shell and taking a while to get to talk to people, but then something else struck me - once you are talking to people, you do actually properly talk to them, as in you're interested in what they're saying, obviously listening and taking it in and giving insight back and suchlike. I can think of some long-term-single people I know who don't really do that, who I suppose are used enough to their own company or something that although it's possible to have something that sounds like a normal conversation with them, you're kind of aware that it's more like discussing a section of their internal topic list than a real conversation. Which is also a useful social thing to be able to resort to and all but it's not as good as the real deal, is it? So, actually being interested in people is an important first advantage that you have, and bear that in mind, I reckon, because that sort of genuine interaction is a good rung on the ladder that can lead to other sorts of interesting interaction. Ahem.

Also, I second the idea of marshalling some handily offhand ways of introducing the concept of you as sexual being, be they ever so low-key and third-party - referring to someone's attractiveness, even if you say that you find so-an-so unattractive - this leaves an opportunity for anyone minded that way to be thinking 'so what sort of person does she find attractive, and is it me, and how do I find out?' Fun fun fun.