Bruce
I've just finished using Hindsight
http://www.hindsight.uk.com/ and it's terrific!
I tried to take some real life photos but they just don't do the product justice - if you want I'll email you them.
Hindsight not only restores your plastic back to almost original transparency, it lubricates by replacing oils. It's not cheap, but in my opinion and in several magazines that have reviewed it, the best and well worth the money.
But make sure that you use masking tape or equivalent to mask off the material around the edges as it's a right pig to remove.
Some comments from their reviewers:
Mecedes Benz Club Gazette
'Hindsight miraculously removes scratches and opacity,and is environmentally friendly'
Total BMW
'Hindsight offers useful long term benefits.If you are restoring an older car then it would be worth spending the extra cash to bring back some flexibility and lengthen its life.'
Porsche World
Benefit of Hindsight on a 911 - 'After about 30 minutes work the entire window came up with a superb finish.'
Autocar
'Scottish Firm invents Screensaver'