Part number is 1K0 511 115 EC for the OE rear springs, Sachs are the OEM supplier for these but their aftermarket code is 994 632 (EAN 4013872854844).
Alternatively you can go the Bilstein B3 (OE equivalent) route which I've done recently, part number for the Bilsteins are 36-148134 for the rears.
You're looking around £35-45 for the springs so budget around £90 for the pair.