Blimey. That's a tall order. 1 litre car engines are always designed with economy as the primary consideration. There really isn't a lot of scope with this. Even if you get 20% (which is unlikely) it's still 20% of, err, not very much in the first place.
Larger capacity engines are often undertuned at the factory, especially modern diesels as they're so capable of delivering huge power increases with little more than a software control data mods.
Commonly known as a remap.
Free flow air filters will give you a little bit more top end breathing (at the expense of more noise). And a large bore exhaust with free flow cat will buy you a little more.
With such small engines there's not really a lot you can do. If you want to get into having heads machined, smoothed ports etc you might gain 10-15bhp. But this will be at the very top end of the rev range. You'll pay big time in fuel costs.
It's also going to cost a few grand to get this done.
Perhaps hold off for a while - get your 1.0 fully serviced so you can drive it to the peak of its ability without fear of doing damage.
Save the pennies and go and buy something a little lustier in standard tune. It may well be enough without mods anyway.