Master or Slave Cylinder

Just wondering if I should pressume that the clutch slave cylinder is u/s rather than the master cylinder on my 88" S3. I'm basing this on the fact that after doing lots of forum searching, it appears fluid running down the pedal is a sign that the master cylinder has gone, or should I not pressume?
Is there any way I can fault find with a certain degree of accuracy before I go out & buy any bits.
Ta, Paul

fluid in the footwell coming down the pedal is pretty much definitely the master cylinder...
if it was the slave it would just leak out under the engine and would not be in the footwell... llok at the location of the master cylinder vs the slave and all will become clear... also a good investigation sometimes throws up other potential issues before they arise

Master cylinder. Change them both - if the rubber seals have gone in one they've probably gone in both and the slave isn't expensive.

What's the problem with yours is it leaking or have you lost your pedal?

I've lost all the pedal. there's nothing there. The motor has been stood a while and I noticed last time I moved it I had to pump the clutch pedal to get any pressure. I just thought its the master cylinder then but reading other posts I'm not sure cause there isnt any fluid inside the car in the pedal box area.
Be nice if it was a leaking pipe I siuppose but I aint never that lucky! Is it best to buy genuine part or will something like a TSW part be ok?

Not the easiest job, either of them - go Girling if you can 'cos you don't want to do this again in a hurry!