This entirely depends on which wheels you go for and what your requirements are. All out handling.......economy or a balance of the two.
Wheel radius counts for a small effect, as you effectively reduce the mechanical advantage that the transmission acts through, although this isn't a huge concern unless you opt for 17's on a Micra.
Wheel mass has a more significant effect with regard to the drivetrain, as you expend more energy while accelerating/decelerating and this also increases the unsprung mass, which in turn puts more load on the suspension system, thus effecting handling.......not to mention the additional loads put through the transmission.
Tyre width can also have significant effect, as with increased width comes increased friction, (great for cornering), however the tradeoff is increased rolling resistance. Increased tyre width also increases the effective frontal area of the car slightly, which coupled with the aformentioned increased friction will further reduce top speed. If you already had wide tyres as standard then the difference perhaps will be minimal, but the difference on a 1.0 for example which had 155 profile tyres as standard, will be much more noticeable.
Collectively, all of the above can have quite an impact on a small engined car.
