Managed to remove bracket today. Here is what I did in case it helps anyone
First image shows double sided foam tape, part doubled over to increase thickness, this thicker side will go to 'bottom' of bracket , towards the window stop
Second shows placed on the bracket
Third shows some duct tape on the side towards the window stop : hopefully will make it last a little longer.
Then trimmed to size and fitted.
( by the way tightening the bolt on the windows slide has helped with the rattling : thanks for all the information on here )