I went for the Fairbourne screen, ordered Monday received Friday & fitted on Saturday yesterday. Fairbourne do not take plastic so ordered over the phone & they sent their bank details. Thanks to Bunny for the tips & Dan for the step drill suggestion.
My screens were not marked 'inside' but there is a bevel on the lower outer edge & this needs to be cockpit side. I found the new screen very reluctant to go in the slot even after I had dressed with a file to open same width full length. A smear of washing up liquid eased it in. It did not say in the instructions but I slid the centre bracket on & tapped home with rubber mallet before marking for drilling. Even though I had taped up the lower protective film I bit got trapped in the slot so I need to find a slim blade to push it down. The job took a bit over 4 hours.
The screens are made from Lexan Marguard a polycarbonate & I could not find a sealant locally which claimed to be compatible so I ordered some Bond-it HA6. As the slots are not sealed I have temporarily covered the gap with masking tape.
I went for a test drive in light rain. I find the above 40 mph the rain seems to hit the centre of the screen & spread out horizontally. I can still just see over or round so I think heavy rain would still be drivable. Moving my outer hand on the wheel up a bit should give more protection. As it could be described as a modification I spoke to my insurance broker & they thought it would be fine.

Tim