I really wasn’t expecting to find this out this morning but I reckon after a little bit of searching if I really wanted to I would have been able to find it!
To turn on the free built in emoji on iOS 5 simply do the following
· Settings
· General
· Keyboard
· Click international
· Select emoji
Job done, now when composing messages, tweets or emails simply click on the globe and you will be presented with nice emoji icons 
Good buy all the apps that used to charge 69p + for apps.