Anyone recomend anything suitable for this.

Basically an old house which i dont want to rip apart to install CH -
currently (old and very large) wall mounted storage water boiler is
mounted just adjacent to the bath and feeds the bath and wash basin -
downstairs has a over sink electric heater.

The bath heater leaks and really is huge (but still works after 30 yrs
use)- i'd like something smaller but still electric powered - are there
any instant water heaters solid enough to run long enough to fill a
bath or are they all storage?

thanks.