right, the 280mm callipers DO NOT fit straight onto non-sport hubs.... sorry but the bolt spacing is slightly different!! whats worst is you cant just change to sport hubs, becuase they wont fit non-sport shafts (unless you get the right centre pushed in, that might work!!)
The easiest and best way is to do a full front track upgrade!! this means getting sport; hubs, suspension, arb, wishbones, steering rack, callipers, discs, shafts.
after which its all just a case of fitting!! then youll have a track thats 30mm+ wider than a standard non-sport offering handling upgrades!!
Or the cheaper option is to try and get non-sport centres pushed into 172 hubs which will therefore fit a non-sport track, but you will still need 172 suspension!! but at least the callipers will fit!!
FAILING THAT (sorry to go on but im trying to give every option) ktec do a non-sport brake upgrade which is a calliper spacer and a 285mm disc!! i used this on my old track valver and it was a really good piece of kit!!
finally, most 15" wheels will fit over the callipers from a sport fine since my sport is sitting on 15's and so are most ph1s! lol