I have a Timber Technicians (Nottingham) High Top with fixed windows. After a month in the boiling hot French sun I'd like them to open to get some air moving up there - the poor kids were sweltering!
Here is a picture of the window (the dimensions of the window - from middle of the seal- is 77cmx18.5cm):

Does anybody know how to do this or where to source such windows? I've been googling but not getting very far.
Cheers