Sliding windows

[Ommm]

We have a loft conversion with a long strip of east-facing glazing. It gets very hot in the morning and the windows are small so it's slow to cool down afterwards. I've fitted 50% window film which helps, but the heat has still got in by then.  The existing uPVC windows also have perished gaskets so the wind comes through.

 

I've been thinking of installing roller shutters on the outside to block the heat. The problem is that the existing windows are outside-opening casement, which will foul the shutters. Inside-opening casement won't work either. Which leaves me looking into sliding windows (openings roughly 700mm high x 1800/3000mm).

 

It seems there are few suppliers of these, mostly in aluminium.  Anyone have any experience?

 

There are some more suppliers of sliding doors - is there a good reason why you can't make a short door into a window?  There are also suppliers of uPVC sash windows - I wonder if those could be used in a horizontal fashion?