I would say 1 window hole (in the brickwork) if its large then its double
I do it similar to that as well. I think of it as £1 per climb for upper floor and £1 per window for ground floor. If I need a ladder for ground floor too I might charge a bit more. Also, if there are a few very small windows on the ground floor I might think of two or three of them as one window. After assessing it like that, I also take a step back and ask myself how long it's going to take me because pricing by windows will sometimes leave a quote too low.
TIP: Never tell the customer that you price per window. Some of them will assign you all the difficult ones and do the easy ones themself.