1.2 Ibizas come with 232mm front discs as standard, you could probably fit 256mm ones which are standard on some other Mk4s (I think the 1.4s?) without any modification.
I'd personally just buy better discs TBH, Brembo make "MAX" grooved discs for the 1.2s and can be used with standard pads. Should improve braking power in theory. When my Ibiza needs discs in future I think I'll get them.
Hmm, no idea about the calipers really! The hubs could probably take it... absolutely no idea about the calipers though.Would calipers have to be upgraded if moved from 232mm to 256mm? (sorry to hijack!!)
not yet, was going to get all the parts i mentioned however with my cusions wedding on the way i need to save money for a suit so unfourtunatly the car has to wait....however i'm sure parts will arrive very soon - they bloody better do i need to do more modding