In an earlier contribution to this discussion,
IMM wrote:


To DIY go combi. they are a doddle to fit and are quicker too. It
will modulate down to the heating needs of the small house. No
complex zone vales or control wiring, etc.

Here we go again - the answer's a Combi - now, what's the question!!!

The OP specifically said that he wanted to keep stored hot water for his
venturi shower - not to mention baths! So, if he goes the combi route, he'll
need to use the CH side for most of his requirements, and use zone valves to
split CH from stored hot water.
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Cheers,
Set Square
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