dont hate them. just believe there life is now drawing to an end. only really hate the vaillant but that applies to combi and system, and thats only because of the time spent on the phone to their "technical" service. more like "librarian"service, when they decide to answer the phone after 40mins on hold. rant rant.
to use any green energy, we need a heat exchanger. only way to convert that into hot water effiecently is a cylinder.
in x years when gas runs out, we will all have sytem boilers.
sytem and cylinder, better flow rates, higher pressure. the way forward
and if the clients bests friends mums dogs got a combi and their brilliant, id suggest to them "well why not go one up on the jones"
shaun