Where I live in the north of England, green woodpeckers are very thin on the ground although quite common down south. I do know of one pair of birds locally but they are incredibly difficult to photograph and even when in a car it is not uncommon for a bird to take flight before you have got within 100 yards of it. The frustration of trying to photograph them is made worse by their laughing call. They spend most of the time on the ground looking for ants but when they fly up to a tree they usually immediately go round to the opposite side.
I was down south last week for a couple of days and managed to find a young one feeding on a grass verge. Fortunately it was less wary than the adults, although still took a lot of patience before it emerged from the long grass bank behind it and I managed to finally get some full frame photographs of a bird which has previously eluded me despite putting in a fair amount of time trying. The photo below was taken from the car. So I still have to try and get some adult photos although this may be a long time coming!!!