I've just spent the last 2 weekends restoring the hood on my spider after it was sat for almost a year and a half, it was covered in mould, lichens and algae. The interior/headlining had a load of mould all over it as well. I started by hoovering the interior and hood (wear a mask), then liberally sprayed both with white vinegar mixed with water (8 parts vinegar, 2 parts water). I left it to dry/for the smell in the garage to go during the week before part two the following weekend.
All the mould inside had gone but there was still a small amount on the roof, I sprayed more vinegar and this time used one of the scrubbers from the autoglym kit to work it in to the hood and then left to dry. I then applied Renovo hood cleaner and left it for an hour before scrubbing it and rinsing it off. There were still a few stubborn lichens that hadn't quite gone so I applied more Renovo locally before scrubbing and rinsing again. Hood now looks like new with all mould and algae gone. Just need to apply the Renovo waterproofer next weekend now. I've got some photos from before so will do a before and after once complete.
The vinegar worked a treat on the interior. After drying out I just hoovered it again and then used a interior cleaner to wipe down all the surfaces.
In terms of autoglym vs Renovo I find the autoglym is good for regular cleaning/maintenance but when the tops needs a serious clean you can't beat Renovo, and now it seems vinegar as well to tackle mould.
2001 Red Alfa Spider 3.0 V6
2002 Lightning Blue Alfa Spider 3.0 V6
2004 Porsche Boxster S (SOLD)