A 1.5 (on our UK roads) could be great IMO but, before that, I'd much prefer that the suspension/chassis is improved for uneven and undulating surfaces. Jazz/Fit has a great suspension on smooth and even surfaces (Japan?) but it gets too easily unsettled/untidy/ragged in its handling on less forgiving surfaces.
A 1.5 with no revision to its suspension could be all mouth with no trousers in many typical UK road conditions. If Ford can get it so right with Fiesta... which I think has torsion beam in the rear, too... why not Honda?
As it is, Jazz's ever so sweet manual gearchange and light clutch helps with the lack of power because it's such a pleasure to shift gears. It's a delight to keep it in the powerband. How many cars have such a sweet gearchange? I've never driven one so slick in its action! Mine's a 1.2 ('59 GE model).