Is it possible to get a bigger gain of power from my 1.2 64bhp engine? Or is it worth not messing with the car and waiting till I can get a diesal turboed Fabia?

Waste of money, no gains to be had, wait for a faster car

Wouldnt bother, its a 1.2 naturally aspirated engine.. You wont get much.

Remaps are only really worth the money when theres a turbo.

All of the above