It may be no better than a combi, as it all depends on the pressure/flow of the mains. It also runs out of hot water, unlike a combi. If a one bath place, I would go for an Intergas combi. Then you release space taken up by a cylinder. With a cylinder you also have more complex, and expensive, when they go wrong, pressure controls on the cylinder. And also complex control with diverter valves on the CH side.