If you�re feeling bullish, try this line with them:
Sirs
I write to you for the fourth time as an exasperated customer and to make a formal complaint. Because of errors with your credit processing system you failed to apply to start taking payments or to keep me informed of the progress of my application. The details you had for me were correct and I trusted you to execute our agreement while I was focussing on personal issues. I was pressured into taking the credit option in return for the insurance you offered and now regret purchasing a sofa from you at all.
I am very disappointed and hope this issue can be simply resolved. If it is not, regrettably I will have to refer this matter to the Financial Ombudsman Service. I look forward to hearing from you by return.
Send the letter by recorded delivery.
http://www.financial-ombudsman.org.uk/default. htm for more info and how to make a complaint.
Good luck.