Change country on app store

I recently went to America on holiday and wanted to download an app so switched to the US app store. I am now back in the UK and have tried changing it back but I have store credit (around £13) and to switch country I must have zero balance. Then I try to spend it but because it's the US store it won't let me download anything! Is there a way to spend/get rid of this balance so that I can go back to the UK app store?