One of the rubber buffers in the engine bay, just in front of the windscreen had split so I investigated.
The rubber was full of water ! It was just like a sponge. It was easily squashed and the water was expelled.
I was able to ease it out without any tools.
I now have two replacements to fit. They have a strip of double sided tape to stick them to the bodywork.

The new items have a hard skin and are very hard like tyre rubber so quite different from the originals.
I can only assume the old ( just 5 years old) were originally hard and have perished.
May I suggest others check them out. I would be interested if others have soft spongy buffers.

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Replacements showing double edged tape and hollows to fit over bodywork bolts
Originals in the engine bay.

 

They are like a sponge material with a tough skin on the outside on my 02. I regularly have to gently squeeze them to expel the water (esp with recent weather)

 

I have fitted the replacements.
I removed the nearest black plastic plug ( on each side) that secures the car wide plastic trim under the windscreen. (the little square plug pulls out , not the whole item.)
I eased the replacement rubber into position and the lifted just the end nearest the engine so I could then peel off the backing paper very gently.
I was able with care to avoid tearing the very flimsy paper and get it off intact.
The rubber part stays in its location so a gently press down on it and it is the stuck to the bodywork.
Put the black plastic plugs in and all is now looking like new.