I have now sourced a screen it was very easy.
There are two options for a new windscreen.
The easiest and best is to contact Roger Williams, Suffolk keep the screen in stock. But having asked the question I also decided to look at the other options
The screens are made by VE Lipponen who are based in Finland and their point of contact in the UK is Master Auto Glass. The factory code for the screen is TRAC001
Contact Master Auto glass via its Director Babak Farsian via e-mail:
bfarsian@master-auto-glass.com, he will then order the screen for you from the factory.
The costs from Suffolk or Babak were the same. The shipping from Roger was more expensive because he made up a box to ship the screen in. Babaks team deliver all over the country and so they are less careful with their shipping because they can always replace the screen at cost. Roger's box is ideal if you decide to buy 2 and keep a spare.
Roger delivered in 3 days, the factory promised 6 to 8 weeks but actually it took close to 16 weeks.
You can also get one made by Pilkington Glass who can etch it with the correct period etching, that is however very expensive.