Found the company in Scotland that Porsche Glasgow use to repair rear Plastic windows. they are happy to deal direct.
Takes 6 hours and costs £295 +VAT Contact Mark Trim Line Systems (Glasgow) Unit 6/7, 636, South St, Glasgow, G14 0TR Tel: 0141 576 0250
Hope this helps someone as it took me ages to track someone down in Scotland that could do this.
Regards
Craig