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Buenchico, my belated thanks for your reply. The reply we received from the TPS states that "Although we have been unable to raise this complaint against the offending company we will make available to the Information Commissioners Office (ICO) details of complaints which TPS were unable to raise against the offending company due to lack of valid contact details." So it seems that your suggestion is actually what the TPS does and that seems to be about as far as we can take things.