Hi Des1170,
I understand that your Office 365 register region is UK, but the address is US address, so when you wanted to purchase license, it failed.
If this is the case, because the register region cannot be changed manually, I suggest you contact support for a billing or subscription issue via http://onlinehelp.microsoft.com/en-us/office365-smallbusinesses/ff652569.aspx.
Thanks,
Eben Liu