Light came on last week, took it in VW this morning for a minor service and to investigate the EML. Called back said it was loss of vacuum in the manifold and the manifold needed replacing. Did explain why my idle revs was creeping under 1k after a min or so.
Iv been seeing this problem alot on the forum lately!
VW quoted me roughly £600 for parts and labour

! I luckily have extended warranty but the VW apparently "didnt know" i had it until i mentioned it to them. Luckily the manifold replacement is included in the warranty and i only have to pay the excess of £250.
I'd recommend getting the extended warranty if you can. This is the second time iv had to claim parts under warranty. first time was rear spring snapped.