OK so after seeing a lot of people complaining about this on Facebook and Twitter for a while, I thought I would post the instructions here on how to change it so people would finally once and for all stop complaining about the iOS Autocorrect dictionary always changing to US spelling.
The fact of the matter is, iOS DOES have a British English dictionary.
Where do you find this such much sought after feature you might ask? Well you can change it by going to Settings > General > International > Language > British English.
Voilà! There you have it.