SUCCESS!!!!!!
Soaked this part overnight, and the following day was able to prize out the domed middle part.
Mir 01.jpg
Unfortunately, the bolt running through this piece WOULD NOT shift. I tried cutting round the inner rim to loosen the washer so I could lift it out (hopefully with bolt attached) - but no luck. Tried to press it out... nothing happened. Tried to hammer it out, during which it shattered! This, of course, released the bolt, and it was no wonder it wouldn't come out - not only was it rusted solidly in place, but it is flared, making it harder to draw through the domed part.
Mir 02.jpg
Mir 03.jpg
This domed part doesn't appear to be available to buy as a single item, so having it all fall apart meant either try get a second hand mirror or try McGiver it, soooooo.. as suggested Pops, I searched through my tin of nuts and bolts and found some suitable bits to use. I put a soft rubber washer (smeared in silicone grease) between the base of the mirror case and the arm connecting it to the door. Where to domed part was I put in a soft rubber grommet (silicone grease again), then a washer, a spring washer and followed this with two small nuts. And surprisingly it all held together (and had a fair degree of movement). Back in with the glass, superglued the black rim back on, and job almost done.
Mir 04.jpg
Mir 05.jpg
Finally, as there was no gasket between the mirror and car door I took an old bicycle tube, drew round the base of the mirror arm and cut. It mightn't be the neatest, but when the cover is clicked on it's all covered up.
Mir 06.jpg
Mir 07.jpg
And hey-presto - It looks like a car again!
Mir 08.jpg
Hopefully it'll last. And should it fall off at some stage, then I'll get a replacement (which I thought I was going to have to do anyway).
Feeling pleased :- )
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