That stuff from B+Q is pony mate, scratches like a bastard and is so shit to work with.

I made my sunroof with the stuff as Plastics 4 performance were too busy at the time i wanted.... usuall for me want it the day before..

If your able to wait a few days i would highly recomend gettin a sheet from the boys at P4P.

Like Lee said(cough cough Nash i mean) run some masking tape on the edge/area you want to cut out, this stops shattering and a little of the dust/melting.

Use a jigsaw with a fine blade and take your time goes through really quick...

P.s this isnt for your windscreen is it im presuming its your rear screen...