Hi jon, just noticed this thread.
I have just replaced my Alternator and decided to do this from above and have in the last few day's finished. The hardest part about the whole job was the removal of the stand bolts especially the ones attached to the manifold.
On reflection i would only worry about the two bolts that are attached to the lower stand-to-engine block (13mm) and free all the wiring and piping and twist it until you can visibly see the upper bolts,(Do not be scared to twist as the stand has a damper joint with a rubber centre to absorb vibration and permits considerable twist even when attached to block)
it will be tight but it will be alot easier than trying it by feel as the only tool i found that i could get on the upper nuts was a spanner.
So! my advice is remove lower two nuts from block, undo piping, unclip wiring and tidy away from stand and direction of twist. Unplug from rubber joins at inlet chamber on engine block, twist closely watching stand below, twist until you can just see upper screws, it will be tight and awkard but it is easier than trying to do it by feel/blind.
PS: Mine is an Alloy Top 2.0TS 16v 150bhp
.....Bit late though!