At least two. With different banks.
If anyone has been following UK news lately they will have seen that one of the biggest banks (Royal Bank of Scotland) suffered a software failure last week and it meant that payments into and out of people's accounts were being delayed by many days. A lot of people got into bad situations because they had just one bank account and no backup accounts or credit cards.
It is most definitely worth having accounts or credit cards with different banks so you can cope if the bank (for whatever reason) fails to give you access to your money.
If anyone has been following UK news lately they will have seen that one of the biggest banks (Royal Bank of Scotland) suffered a software failure last week and it meant that payments into and out of people's accounts were being delayed by many days. A lot of people got into bad situations because they had just one bank account and no backup accounts or credit cards.
It is most definitely worth having accounts or credit cards with different banks so you can cope if the bank (for whatever reason) fails to give you access to your money.