Is there a difference between the brakes on a pd100 fabia and a vrs? 

Will octavia vrs mk1 carriers fit on a pd100 hub? 

Thanks 

No, IIRC the PD100 has FS3 front brakes which are 256mm with carriers integral to the hub assembly.

^^^ What he said. You'd need 2.0 petrol or VRS hubs. With VRS hubs you could then go to 312s or bigger depending on wheel size and anticipated usage. If you go for 288s, be aware that then upgrading to 312s also requires changing the calipers. In this respect it's different than the MK4 (Golf), where the 288s and 312s use or can use the same calipers.