I hope this is of some use to somebody, but I have just had my alternator fail on my 160,000 TDI Octavia. I was just pulling on to the carpark at a customers, when there was a clunk (the freewheel pulley had seized and come off!) and the battery light came on, and steering got heavy. Anyway, after much searching to locate a replacement alternator, (they can't get them at Halfords, and Skoda want £270! even recon ones are £170.) I had to remove the old one. The way I did it was to undo the earth lead on the battery first, remove the engine cover, then undo the power steering pump and the bracket which holds the rigid pipe (makes it more moveable) to move it out of the way, undo the tensioner, removing the pulley first (easy job, just 3 x 6mm allen bolts). I pulled the belt out of the way from underneath, having first removed the undertray, and disconnected the alternator wiring. I undid the radiator fan, so it would give me more clearance, and having undone all the bolts for the alternator, was able to squeeze the alternator up through the gap, bending the radiator hose out of the way. This all sounds simple, but as it was trial and error, it took me about an hour. I think you could do it easier by removing the a/c pump and dropping the alt out through the bottom, but I thought it looked trickier to locate the bolts.
I am still to put the new one back in, so if I find any problems I will add to this thread
Cheers
Neil