As for cc you could try for a money transfer card that allows you to transfer £ to you bank account, or you could try for a loan with a lower APR but that might depend on your income.

There are different options - all with benefits and disadvantages.

It is unlikely that Black Horse will accept credit card payments so you would need a money transfer card to transfer the money to your bank account and then pay it off from there. That would allow you to pay it off at 0% for the length of the offer.

Risks are:-
Unless you're a high earner with a good credit history you are unlikely to get £12k as a limit.
There will be a fee. It will vary but could be 3%
Watch minimum payments as they vary for different companies and you will need to meet at least them every month.
The standard rate for the card could be high. Certainly likely to be higher than 11% If you haven't paid off the loan by the end of the 0% period you might not get another transfer at 0% if your circumstances or market conditions have changed. Then you'd be stuck with higher rate.

Personally I'd go for it - try an eligibility checker for the chance of approval and apply for one which has a high chance, but you need to know what you are doing and the risks.

A cheaper loan might be an option if you are eligible. The best rates are around 3% which would be a substantial saving, but you might not get one.

Another option is overpaying. At 11% over 8 years if you overpay £100 now it will save you over £80 in interest. That saving will reduce for subsequent £100s as you reduce the term and it reduces with the passage of time but it will still be very much worth doing.

The only thing I would add to the above reply is to ask Black Horse if they charge any early repayment charges as some do. I agree with Nebulous2 that its worth trying to get at least something on a 0% money transfer card and cutting the debt. Maybe try a loan eligibility calculator first as a cheaper loan over a longer term than a MT card may help you pay it off quicker but not fall foul of the 0% ending. I just got an MBNA all rounder card and there offer is 20 months so its not long on a large balance.