I will answer my own question in case someone comes across it in a future search. These are the brackets I was trying to move from one bumper to another and I thought I had to undo the height adjuster screws which you may be able to see are riveted over on the ends. On closer inspection there is a T40 Torx screw accessed through a hole in the bracket attaching the U shaped bracket to a captured nut in the bumper. With all the foam etc I thought the U shaped bracket was moulded into the bumper. Removing this screw the whole thing can be transferred to the other bumper. Now if I can only free up the height adjuster screw on the other bracket. (this one alredy done.) David