I live in the scottish borders. It's very rural and there's a hell of alot of fussy customers. Anyway, i usually charge 50p for your average sized window. If it's twice the size, then guess how much??
Doing this i can earn about £20 an hour. I don't rip anyone off, but on the other hand, i'm not a charity! 2 up - 2 down is 4 quid. Thats pretty much the same for us all round here.