Hi Maddy/Lindal, thanks for getting back to me.
I already have Advanced/Hi-Res Snapshot enabled too, however the missing element was clicking on the first pull-down and selecting "Custom". It's so obvious that I want to save the "Current Window" I'm always forgetting that actually IS a pull-down.
No, Lindal, you're quite correct that I won't get any more detail than the maximum pixels of my monitor, but I'm cropping the shots later and that is where I then reap the benefit of having a higher detailed original.
Anyway, thank you both again, and i hope I've posted this reply in the right place.....