Compansation not received

Having admitted in writing their mistakes Sky TV company offered me a compensation of £50.00 on 20-07-09 which I accepted to get them off my back.I received two letters dated 20 July 09, one saying that the £50.00 compensation has been arranged and the second letter saying that the cheque is on the way and should be received within 14 days.When nothing received by 23August 09,I sent a reminder with photocopies of their two letters to which they replied that my request has been processed.I,finally wrote to them that their reply is not satisfactory and I intend to approach the regulatory authority and if needed seek legal help to which I have not received any reply to date.Please help me by letting me know who do I complaint to?