Dead Hotpoint WD645

A service engineer from Domex UK called round this morning and diagnosed the problem thus; “It’s the computer”. Upon pressing him to elaborate, he offered “not the one on the front, the one at the back”. Does he mean the power module? if so, could this be a legitimate reason for the machine – which was fine when switched off at the end of its last wash – to now be completely dead? I checked all the obvious (fuse, power supply etc) and they were fine. I’m slightly dubious about the diagnosis as the fellow, at one point, was testing the on/off button with no mains power switched on. Am I being paranoid or does it sound like a perfectly reasonable diagnosis? Thanks for any opinion you may be able to offer.