I have a UK thread running discussing the 'ins and outs' of soft top replacement as I'm also about to replace mine. See here:
http://www.mbclub.co.uk/forums/showthread.php?t=26860
It's a long thread I know so here's a précis:
There are two rear window (flex-glass) manufacturers used in the manufacturer of R129 soft-tops: Gurit
http://www3.gurit.com/auto/products_wopavin.php their material trade name is Wopavin and Polyone
http://www.polyone.com/bizunit/films/films_reg_spec.asp ULTRALITE BUV.
An example of ULTRALITE BUV fitted:
http://www.mbclub.co.uk/forums/showpost.php?p=261911&postcount=67
Now here's the interesting point, Mercedes OEM material is Wopavin at a thickness of 1.25mm for the center window and 1.5mm for sides BUT Gurit only supply 1.0mm to ALL UK manufacturers!
I know of two European hood Manufacturers who have confirmed they use both the original sonnerland canvas and correct Wopavin thickness.
These are:
Aresma GmbH. Cost 615 euros plus 37 to ship to the UK
They will also supply just the flex-glass
or
EUROTOP GmbH & Co. KG, Mühlstr. 16, D-72622 Nürtingen, Deutschland / Germany
Prestige want 14 hours labour for fitting their hoods which in my opinion is excessive. Typically it's around 5 and it's NOT a DIY job - I have the video clip if you're keen!
Hope this helps some
Lea