Not sure precisely what kind of macrolepiota they might be.
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Some fungi are very poisonous so a mistaken ID could have serious consequences.
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See if it looks like http://www.ispot.org.uk/node/235832, another large floppy parasol.
What did the cap look and like how coloured was it?
Thanks Martincito and Flaxton for taking the time to reply. I've added another photo that shows the top of the mushrooms (I missed this one when I first posted the observation). I hope that clears things up. Looking again at the photo I just added, the mushrooms appear a bit more colourful than the M. Konradii in your link Martincito.
The caps do show the cogwheel- or star-shaped central discs associated with M. konradii (Collins guide) :-)
Whith this pale colour it could also be Macroleptiota puellaris.
That one is new to me, and rather tricky to track down in the books, presumably to a series of name changes. It certainly looks like these photos from what I can see on the web. The latest name for it that I can track down is Leucoagaricus nympharum...
That's the one. It is almost totally white with a slightly darker centre.
Lat/Lng: 52.29093, -1.51364
OS grid ref: SP332659