Harry Bloomfield was thinking very hard :
Split temp, yup see my other post. If Gremlin95 is about, he knows more
about the new range than I do.

Yes, that's it, 'split temperature' was the expression I was seeking. Thanks
!

Having enquired with both Worcester and Vaillant, neither offers a
regular / conventional boiler which includes an ability to set two
separate output temperatures for heating and hot water. A gap in the
market me thinks, for an enterprising boiler manufacturer.

A single boiler setting stat is fine, where a consumer is happy with a
lower temperature of boiler output for both heating and HW, but less
useful for someone like me who likes their HW hot - where there is a
possibility for some saving on keeping radiator temperatures lower, so
the boiler remains in the more efficient condensing temperature range.

I suppose I could do an add-on stat, mounted on the flow pipe to the
radiators, to shut the boiler down at say 60C leaving the boilers own
stat set to maximum ? Would that not wreck the boiler's efficiency?

My current scheme is to manually tweak the room stat, gradually raising
the room temperature to the desired temperature, over a couple of
hours. Otherwise the heating system over reacts if the stat is set to
desired in one single movement of the dial.