Corsa B Brake upgrades

[Kaison]

Just brought a Corsa B, need to replace the discs and would like to go for something better than standard and I believe I remember people using Fiat Coupe Turbo discs?
Is it possible to fit these without issue or modification? Was thinking of going 284x22mm rather than 304mm? - £20 price difference on Ebay!

[Nemesis]

256mm brakes give the best feel as the calipers aren't too big

If you want bigger, use 288mm 4 stud discs (Meriva?) and Calibra/Cav turbo calipers/carriers