Brand new? Pretty damn expensive (hundreds per caliper), I grabbed some MK6 rears with very low miles on the bay, they are slightly different, as the Mk6 does away with the hard pipe to the caliper and is soft from the main line to the caliper.
If you've never done them before, it's probably easiest to grab a Mk5 rear for direct replacement (although it's not much longer to swap out that section). Should be able to pick up a lowish mile mk5 caliper for about £40 or so. You don't need to change the carrier for the mk6 caliper or mk5 caliper to fit, but you can if you want to, I didn't bother - as I was in and out of the hail today.
It's worth noting a decent indy shouldn't charge a lot, perhaps £40-£60 per caliper.
If you do decide to do it, make sure you have some Plusgas or similar
I grabbed a quote from VW for complete replacement of all calipers including labour... lol, are you sat down?: £1600!! Did it myself (albeit with low mileage 2nd hand parts) for £200. Well worth a waste of a Sunday.