Hi @Pattidabrass,
Thanks for the additional info. On Xbox you're billed by Microsoft so I would either make sure that there isn't some kind of parental control on the account or I would check that the information on your credit card matches the information on your Xbox account. For instance payments may fail if the account is registered in the UK but the address of the card is in the States.
Other than that, it could also be a connectivity issue so if you're using wifi, try to connect with an ethernet cable and / or reboot the modem for a minute or two in order to refresh the connection.
Let us know if it worked.
