Had a look through the archive but still have a couple of questions.

Gas not being an option unfortunately, looking to replace header and
immersion tanks with some form of `undersink ` heating. To supply kitchen
sink and showeroom basin , replace current dribbling shower pump, non power
shower :-( , with electric shower.

Uvented Undersink appears to mean under a sink at least 4 meters away for
some models though, is this total?

Or can you have a tap tee`d below the 4M limit but overall pipe length to
second tap extends to the limit?

Is it better to have a the heater at the washing machine/sink or
bathroom/ex-water tank space?

Is a copper tank heater that much better than a Screwfix

http://www.screwfix.com/app/sfd/cat/...37130&id=68643

type thing, enameled steel tank?

Is a 9.5kW flow boiler a better solution?

Thanks for any help.

Adam