Today, I found two huge patches of Shaggy Parasol Mushrooms (Macrolepiota rhacodes) near the compost heap. The photo shows one of them. There must have been about a dozen of them, all about this size - more than 4 inches (10 cms) diameter.
These mushrooms have brown scales on the cap and a bulbous base to the stem.
They are apparently edible, but can cause stomach upsets in some people. I should stress that you should never eat any fungus unless you are certain it is safe to eat.