The BBC’s Watchdog programme (series 38, episode 1) did an excellent job exposing the activities of a company called Energysave, which was caught training its salesmen to use high-pressure sales techniques on vulnerable customers. They were claiming, outrageously, that their product, a water-repellent coating for masonry, cut heat loss by a third. (Although their website says conductivity “decreases enormously with dampness”. Whoops)
You can catch up with the episode on BBC iPlayer. The relevant material is in two parts at 16’04” and 32’53” with the final confrontation scene at 51’52”, but the episode also includes stuff on defective smart meter installations.
Thanks to newsletter reader Istvan Sereg for the tip-off.