It is Rubbish, absolute rubbish!! If you as an electrician were so easily fobbed off with that kind of crap, then more fool you!!
This has come up on here so many times now. Let's get this one straight once and for all!! The only reason manufactures fit a plug to appliances up to a certain rating, is to do with EU regulations, in that manufacturers must fit a plug to appliances that is suitable for the country of final destination. It has nothing to do with any end user warranty!!
A manufacturer cannot and will not invalidate ANY appliance warranty, if the appliance is connected to the supply by a means that is recognised as compliant by BS7671, or indeed any other countries compliant methods (the same models are available throughout the EU and the plug tops won't incorporate a fuse!!).
What your talking about, are these warranty service agents that some manufacturers use, that think they are above commercial/consumer law. They often try it on with the general public but, i can assure you they have no legal footing to do so., It's normally based on the fact that the service engineer sent round to sort out a problem with an appliance, can't be arsed with disconnecting say a FCU or CCU. So they try the warranty invalidation angle/stance!! Further, i've personally never seen a manufacturers warranty that stipulates removal of a plug top will invalidate said warranty. If it did, it would contravein UK consumers rights, and could be totally ignored anyway!! lol!! Maybe different if the end connection was DIY hack job, and left in a dangerous condition. Even then, once restored to a compliant connection the warranty would continue!!!
There was a member here who's wife is a solicitor, and confirmed that manufacturers have no grounds to invalidate any appliance warranty purely on the grounds of the removal of a moulded (or otherwise) plug top. The appliance has to be fit for purpose, so any component that fails (ie element, switch, pipe, pump etc) during any warranty period issued by a manufacturer must be rectified, or replaced....