Our Britony IIT (about 10 yrs old) doesn't fire up unless the hot tap is opened almost fully. It's always needed the tap to be opened most of the way, but I've just put in a new kitchen sink and monobloc and it splashes too much with hot tap that far open. Should this be fixable if we get it serviced? And generally, is there likely to be any justification for the service engineer saying the whole thing needs replacing? Just want to be prepared!