I just tried BoilerJuice thinking it would save a lot of time and calls, but their price range today for 1000L (in Worcestershire) is £39.75 > £49.99, whilst my supplier is now quoting £32.95 (they were nearly 10p/L cheaper than anyone else last time around). I checked whether my supplier knew of them. Their reply was, "yes and we're registered with them, but they will always be more expensive, because they add a charge to ours!" If that's the way it works, it's not quite the same operation as the more widely advertised comparison sites for other services.