Crem, try phoning the manufacturer (if you know the make and model) and they will give you the exact measurements. It's always something obscure like 2470mm x 7130mm and it has to be right! Our local greenhouse shop has a 'man who mends'. He fitted my glass and tied mine down to the patio for a small sum, thank god. Honestly, if he hadn't done all the tying down and drilling in, my greenhouse would have been half way across the garden after Friday!
Having a lovely peaceful day here, baking with dd2. Off to visit my dad who starts the conversation 'Well, if you are passing a shop, could you .......' so it's off to Sainsbury's on the way.
Dd1 back tomorrow - can't wait to see her, assuming planes are leaving NY at the moment.