They offer a "same-day" repair plan, too. In the advert, calling by lunchtime gets them the same day; in reality, you call on a Friday, they'll show up sometime on Monday. That made last winter "interesting" as headed for -20...

(To cap it all, the problem turned out to be their own installation error - then last September they offered to fix it properly for an extra £140 so it wouldn't break down again this winter.)