How could I simulate glass for my french shop dio

Any hobby shop that sells sheet styrene will usually have sheet clear styrene as well.
But keep an eye out for any item that is bought for household use that has flat, clear, stiff plastic. It can also be used, using white glue to fix in place.
Clear overhead sheets are another option. You could even print out some details for a shop window on it, and then cut to size!

Gday Matt
Ditto everything Frank said... clear shoebox lids, plastic action figure bubbles (on the backing card),
Warriors figures come in a clear packet... Just cut out the flat sections needed. You will start to notice it every where you go

To simulate broken and shattered glass on the ground try using the small pieces to thin glass that they use to make microscope slides. (it's the really thin piece that is placed over the material that you are viewing) At any rate, it's very thin, easily broken into small sharp pieces. Attach with white glue and don't run your finger over it when it's in place
Cheers,
C.

I'll ditto C, there was some broken microscope slide glass in Biology which was heading for the bin so I "rescued" it, :-) and although I have not used it, it is really thin and the pieces are very realistic!

Harry