if you look in some of the sierra handbooks, you will see a 1.8 sierra with abs

the S2's used the same brakes as the sierra's that had abs (and the same size as those that had discs all round)
they are the same size on the granadas but they have an extra hole in them to acomodate the extra stud in the hubs

don't buy sierra 4x4 discs as they run a different offset
don't buy sierra cosworth 2wd discs as they won't bolt on without a spacer bracket
don't buy sierra cosworth 4x4 discs as they are so the wrong offset

the calipers on the granadas and the sierras that use the 260mm discs are the same as on the S2 so if you want to upgrade to 260's and DON'T feel the need to go and look for abs specificly equied sierras, just go and get the ones from a granada