Quick question, would it be possible to take the rear hub disks and calipers from a mk2 scirocco?

Assuming they are the same as the mk2 Golf which I think they are then yes.

You'll need everything from the stub axles forwards. Pretty simple conversion in regards to bolting everything on. The tricky bit is the handbrake cables and the brake lines.

You can get adapters online for the cables, but can't see any on eBay just now.

Here is an old link anyway http://www.ebay.co.uk/itm/MK1-MK2-Caddy-Inca-Rear-Disc-Conversion-Handbrake-Cable-Spacers-/111620827635?pt=LH_DefaultDomain_3&hash=item19fd1ea9f3

You'll also need to relocate the cable holder things on the rear beam, but this is easy enough, they just unbolt.

If you do the conversion though you'll want to look into fitting mk4 Golf rear calipers as they are less likely to seize than the mk2 style ones. But then you'll also need a conversion kit from Goodridge as the mk4 Golf calipers use a banjo style fitting unlike the mk2 Golf.

this was my conversion

http://w11.zetaboards.com/Polo3/topic/10853609/1/