I was very pleased to see and read this thread, I had precisely the same issue a couple of others have mentioned.
I had my 95 X300 in having some minor damage repaired to the rear bumper. The repairer claimed it took them over a month to find a replacement, Bumper chrome however I suspect they were charging my insurer for the loner I was driving during the repair, hence their lack of motivation to finish the job quickly.
Anyhow when I finally got it back, I pulled up in front of my letterbox to get the mail, as I got back in the Top hose came off. On inspection, I realised the plastic lip on the spout had snapped off and was partially still stuck in the hose. I say I am happy to hear others report the same problem as I have always been a little suspicious of my repairer as they had, had my Jag in their shop for over a month and the radiator appeared to otherwise be in perfect condition. I made some inquiries and apparently the radiator header is not replaceable as a separate unit so I swapped my radiator out for a good second hand one. One radiator shop I spoke to, suggested I put a couple of short self tappers around the end of the spout to give the worm drive clamp and hose something to grab on to.