Despite asking about extra costs and being assured the company would 'take the hit' if anything did arise I'm still without heating because a valve has failed that controls the heating side of the system. (Beware small print.) Being a pensioner I am not able to instantly produce spare cash for unexpected 'extras'. But hey! I'm just an old woman who now has a little more knowledge about heating systems, I've survived the 'beast from the east', spring is here and hopefully funds will be found before warmth is again in demand. Maybe Impragas will also clarify the statement in their brochure regarding hidden costs and think about principles.