No my feeling is it's not a problem with the boiler. It sounds to me like if the boiler gets 240v it will all run as it should, therefore my question (assuming nothing) is, is it indeed getting 240v? As it's a Y plan, is it wired up properly, which you might not notice if you fault find with a glowing screwdriver rather than a meter.Hufty, never seen these suffering from stray volts like Wooshitter Botch.... Have you?
Customer: wasn't suggesting you test this yourself, it was more a question for the installer.