My drivers wiper blade must have picked up some dirt as its scratched the screen is there a product i can use to try & polish it out or is it new screen time? 

if you can feel it with your fingernail, then it will be new screen time.

Mine did the same when the guys were taraccing and picked up a damn stone, not even that big to be honest. Nice arc shape scratch on my windscreen. When it does my head in I will get it swapped out.

It will polish out if it's not too deep with some proper glass polish and a machine polisher

There is a glass kit I use with my rotary polisher. At high speed it got similar scratches out my dad's A3 windscreen. Essentially like a jewellers rouge stuff.