Having found the Fair Use policy with it's 75GB cap I've now also made a complaint to the ASA.

An update: ASA are carrying out a full investigation.

Go ASA about misleading advertising but what about the inital disclosure of personal information by the estate agent?

Unless you explicitly gave permission for your details to be passed onto Home Telecom, or other 3rd parties with potentially useful products, then I believe that the 1st Principle of the Data Protection Act has been breached see here and scroll down to:-

�be transparent about how you intend to use the data, and give individuals appropriate privacy notices when collecting their personal data;

�handle people�s personal data only in ways they would reasonably expect; and

�make sure you do not do anything unlawful with the data.

See here for the ICO's FAQ on passing data on without consent and here for how to register a formal complaint.