I copied this text from the offending web site

Maybe if we inundated them with phone calls it might help?

Q. I don’t wish to receive any further mailings from you. How can I have my address details removed?

A. Either write to us at Dept. MPS, Green Heys, Walford Road, Ross-on-Wye, Herefordshire, HR9 5PQ or telephone our Customer Services helpline on 01989 769797. We will remove your name on the same day we receive the request. Please note because of processing time you may receive one further mailing from us after your request.