Steve
I had a similar problem and spoke to several people about resolving it. Based on their advice and research I did elsewhere I used AutoGlym's Cabriolet Fabric Hood Cleaning Kit on the hood itself and a product called Hindsight.on the rear window which had become cloudy and also had a couple of patches of milkiness. Neither the Autoglym nor the Hindsight were cheap: around £18 and £40 respectively, but FWIW, I was very impressed - especially with the Hindsight.
www.hindsight.uk.com
I have no involvement with either company.
BTW: you may find the following link of use - it's for Peugeot cabriolet owners:
www.pcoclub.org/
HTH
Dave