Had the offer of 2.5L of concentrated screenwash 2 for £2 or £1.50 each.
They scanned through at £1 each anyhow. I have used this for years and is as good as any other, and as its concentrate, its (IMO) better than buying the pre-mixed stuff as you can add as much as needed with water.
So stock up before the winter months before the price goes back up and it sells out just as you need some!
Even better buy some and keep one in the car, so when you do run out you wont be left without something to get the muck off your screen!