Store room catastrophe... and more mushrooms

I was next door having a nice cup of tea with the neighbours when Ian turned up, saying, We have a problem in the store room. The shelves have collapsed. I rushed home and this was the scene that greeted me:

Aftermath of shelving collapse

Actually, that's not quite true. The first thing I did was pick up the demijohns - thankfully not broken, in spite of having been on the top shelf - to see if anything could be salvaged of the contents, and ditto the air-locked bottles of blackcurrant wine. Ian also refused to let me mess around taking photos until I'd dealt with anything potentially explosive. If you look at the right hand edge of the above photo, you can just about see the escaped stopper of the one glass bottle of pink elderflower champagne. I also had two glass bottles of not-pink elderflower champagne, presumably equally pressurised. These were carefully removed and depressurised outdoors - they didn't seem all that explosive, actually.

So... these had been salvaged by the time I took a photo of the chaos.

Almost a demijohn-full of oak leaf wine, just over a pop bottle-full of blackcurrant wine, and two intact bottles of elderflower champagne

It could have been worse. I'm putting off dealing with the rest of the mess until I have somewhere to put things. We now have no shelves in the store room at all.

At the same time, elsewhere in the store room, I spotted these:

More mushrooms growing in the store room

This morning I went down and picked one, so I could take some better photos:

I've looked at a few websites, but I can't identify it. Any ideas?