If you have the 239mm discs then that is the size to order, the caliper carriers are different for the 260mm discs, so if you try to fit 260mm discs they wont fit without using the matching carriers for the bigger disc, on the upside you can use the calipers you've ordered with the smaller disc.

just fitted a set of Rugby rover new 180 calipers. Just about all good :weakbench:

One Banjo bolt was very tight but other than that, should be the last caliper I ever need for my 180.

All painted yellow to match the new fronts from big red.

I have calipers from him on the rear of the ZS and the ZR and all round on the MGF.