wrong language (admin control panel)

Hi, can anyone tell me why in dashboard-settings-general the site language refuses to accept english(UK). Its on the dropdown with a few other languages. The others work. But eng(uk) does not, it keeps going back to Eng(usa).
I installed eng(usa). Got all the .mo and .po files for other languages and uploaded them to content/langs. So whats so special about the English?

Any tips please…