I think you might have cracked it!!! In fact it also makes me think i did find a young one - i just didnt put it together. Im going to update the post later to include C.cinerea and the picture of the young mushroom - but excellent job - that species fits the bill more closely all around except perhaps a thicker stipe than what i saw - but that sort of thing is variable enough that it still fits the bill i think.
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RE: The Amateur Mycologist - Random Find + Awesome Photos [OC]- Probably Coprinopsis cinerea (thank you @fabulousfungi)