having been bold and cut the canopy out of the main body, the next challenge is to make the screen fit. Rules require perspex so it is shatterproof, quite rightly, but shaping the stuff is more tricky. Mr Google told me that i needed to get it to 170oC to be able to bend it nicely. tried an airgun, and it was hopeless, far too localized and not really very controllable. Found a small piece and popped it in the wifes oven whilst she was out, and hey presto, 10 mins at 170 and its soft and malleable, result, apart from the screen is too big for the oven at home.
Then o had a lightbulb moment, my friend and ex-work colleague runs a lovely pie shop with basically a pizza oven in it, and this is massive in comparison, so trip arranged after normal shop hours, and literally 25 minutes later i have my nicely profiled screen ready to cut and fit to the removable canopy - Thanks Stephen.