Oh right, I wasnt sure if it was 2 or 3.
I see your problem then, maybe theres been a repair there before & it was tiger sealed on (if it wasnt done properly it might have made it retain moisture).
I`ll have a look at mine tomorrow to see if its sealed on or not, I know in my Panda it was just held on by the rivets & still fitted flush with the metalwork.
The 1 time I took a door rubbing strip off an Uno, it was sealered on (& it hadnt been touched from new), but I dont think they`d have glued the arch trim on (or they wouldnt have bothered with the rivets).
If it is tiger sealed on, you might have to resort to a long blade, but you might get away with a strong nylon fishing type wire, used like a flexible saw.
Cheers