I can't get my I tunes back to uk from USA, I have a gb logo on my Ac. Pls help thank you

I've added an aps to my I tune and it asked me to change from ok to USA, so I have done this. I am now unable to have any new aps as it keeps saying my I tunes is USA and I need to change it back to uk. I have looked at account and it is showing a GB logo and not USA. Can any one advise me on how to get my I tunes account back to uk please.