This is not individual financial advice under the Financial Services and Markets Act 2000.
You mention that you have a bad personal credit history (such as previously borrowing money and having difficulty paying it back) and that you have a mortgage.
This may help getting a business bank account if your payment record is good and if you have some equity in the property.
However, if you are running a business you will definitely need a bank account for payments. Some banks offer basic bank accounts for credit impaired people.
But it will come down to whether they think you are a good risk or not.
NatWest and RBS have a product available to entrepreneurs who have previously been unable to open a business account.
It is called a Foundation account and offers a chequebook, cash machine and Solo debit card, standing orders and direct debits.
Abbey National Instant Plus offers a current account with a Visa debit card but no chequebook.
Halifax offers a chequebook and cash card, but I have no experience of seeking a business bank account from any of these providers.
If unsuccessful with the banks, you may be able to get an account through a broker. But be aware that lenders to credit impaired people usually offer worse terms than to people with good credit histories.
Also bear in mind that If you apply to a number of sources it may further damage your credit record.