Gents thanks, a lot of good input, yes John V6, i now see lorne on Gomog has got much useful experience and suggests getting one cut to profile and size although fitting was a challenge. I didnt have that problem of fitting one to the Caterham.
Its all very well passing it over to your insurance company if your covered but if the repair isn't executed expeditiously and you get an experience like Kev Fitz you could be Mogless for half the summer season. I had a screen replaced on my Elise a few years ago, phoned on the morning, screen replaced on my drive by 14.00hrs same day, thats the sort of service i was expecting.
I may investigate getting a glass cut, and do without the electric demist facility, show me an MOT tester who'd check that!