I use a mix of English cider and I've been getting wild yeast recently too. In the end, I'm probably getting more wild yeast then English Cider these days. I have heard that slow and long give better tastes so I make sure they are active, then put them in my basement for a long slow ferment.
To clarify what bottle rocket said... 19C=66F, 22C=71F, 24C=75F. I agree with bottle rocket about the temps. I've also heard that wild yeast like it colder.
As far as how I get wild yeast... I use campden and still get growth. I'm guessing that campden does not kill everything and the yeast around my house are just tougher. I've done this for the past two years and do not get bacteria contamination but do get dry, very well fermented and very tasty brew. I've never intended to find wild yeast, they just appear and I don't complain.