On Wed, 31 Mar 2021 17:11:54 +0100, Mike Halmarack
wrote:

snip

I think I
would prefer to go for the flash/instantaneous option, even though the
power supply would need to be hard wired.

A mate replaced the 'boiler' type water heater for an instant oversink
type in his shop:

https://www.tritonshowers.co.uk/t30i-handwash

And hasn't regretted it for a second.

It was easy to install, didn't necessitate having to modify the
existing tap feeds and can be run as long / often as he needs (which
has turned out to be quite a lot because it's a shop that's considered
an essential service so open during lockdown and Covid itself).

He said it's at full hand washing temp in about 5-6 seconds but as
it's a spray that's not a lot of water. And that's why I was
interested in something like that as my bathroom hand basin feed is
reasonably long from the multipoint gas water heater, in 22mm copper
(for the bath when there was going to be indirect HW cylinder there)
and whilst we aren't on a water meter (yet), do try not to waste any
if possible.

Cheers, T i m