Polo 9n 1.2 few questions

[Turbocod]

Hi all, thanks for the add, recently bought a red 1.2 6v 9n3, which ultimately will be my son's car, but have been using it to find what needs sorting on it, and a few upgraded parts too.
OK, so first up is the eml light comes on, can turn it off with vcds lite, and gives codes pointing to lambda sensors, a fuse blown and replaced the pre cat, but code p0130 went, then came back, and codes P1118 & P0140 which are post cat, looks like there is a bit of dodgy wiring near plug for sensor 2, so hope it just means a rewire of both sensors.
Next questions are to do with brakes, upgrade to be precise, Rear, can I fit disc and calipers with new cables to replace the drums? Seems easy, has abs already.
And front, can I use hubs/swivels off of a polo TDI/gti, fabia Vrs or an Ibiza 1.9tdi/cupra? Looks like outer CV splines and seal size are same as 1.2 CV just inner driveshaft fitting different? So I can fit larger calipers/discs off golf etc.
Thanks for help, sorry I've only had a mk2 caddy and an A4 previously in the vw stable.
Cheers Dave