A small bit of advice to peeps who have been locked out...
If you find a spark plug, keep the white cermamic peice inside it, not the metal piece, sharpen it up with a wall or a hammer etc and throw it as hard as you can at your desired window.
It will shatter the window instantly and you can walk in
I found this out because at a tip in my hometown, a guy had trouble getting into a wrecked jaguar so he got a peice of the spark plug chucked it at the side window (and bearing in mind its toughened glass) shattered it totally