A stage 1 remap (software modification only) will see you go up to about 130bhp with the 1.2 engine - it would be fairly nippy at that point! There are lots of different tuners out there who offer a variety of products, some are permanent remaps, some are plug and play tuning boxes that you can easily remove.
With a custom exhaust and performance air filter you could probably squeeze out a few more bhp but these are more for the aesthetics/sound.