Providing you are not on any sort of AVS schedule, I'd use any full synthetic 5W/40 such as Halfords (was on buy one get one free last time I was there - so that's 10 litres for £33) or Synta Gold (about £24 for 5 litres from GSF). I use either of these in my S3 and in my Ibiza, changing it every 5000 miles / 6 months.
If you are on AVS then the manual should tell you which one of the various specs you need to use - but expect to pay a fortune for it (like £10 a litre).