Humm.... that took some finding, but i knew i'd seen it somewhere...
Here you are, it's a Ring Pull Slam Bolt!
all for the grand sum of £4.32 each
http://www.europaspares.com/exterior...slam-bolt.html
Additional to that, Woolies also have another option for those who want a "big handle" type:
http://www.woolies-trim.co.uk/p-1827-door-lock.aspx
This is what i'd originally had in mind for mind, but i'm not sure atm...