For what is worth, there is a pdf file here:
http://24december1944.com/wp-content/uploads/FO587.pdf
On the last page (page 7) under Information for Scouting Force there "appears" (if I am reading it correctly) to be a list of target codes with co-ordinates.
GU-4048 appears to be Ettinghausen (actual co-ordinates) 50°28'42"N 008°38'26"E
The next code, GU-3963 appears to be the airfield at Kirch-Gons.
You can possibly check some of these in the site:
https://www.forgottenairfields.com/index.php