Thanks both for the encouragement
Well yes of course it's a little scary at first.. I was super nervous on 1/100!!
My plan of action when planning on getting a shot:-
In the office, get my camera set up, I'm now set on f2.8 / AV mode / ISO100 /Spot metering / One shot focus.
So my camera is ready I no longer have anything else to worry about other than approaching someone (I'll take a random test shot outside and check the histo).
I then walk to town.. confidently (or look confident), knowing that I'm not a weirdo with a camera, I'm just a normal chap who deserves to be there.
I see my stranger, and approach them, I try to ensure they've seen me, and made eye contact (whilst I look confident / friendly / smiley).
''Excuse me, would you mind if I took your photo for a photography project that I'm working on?"
"...erm....ok"
"Don't worry, you won't appear in the sun or anything daft!"
etc etc...
Then I try to make them laugh whilst shooting them.
Job. Done.
I hand them a card with my flickr on and scurry back to the office!