Christina Websell wrote:
Google for parasol mushroom+images.

Tried that, was googling and wikipediaing for quite a while without turning
up anything that looked right. Hence hoping someone on here might recognise
the description

I would not like to advise you whether or not it is poisonous.

I wouldn't be trying it even if I was 99.9% sure. One day I may try the
mushrooms that grow out there because they're definitely field
mushrooms, and my neighbour has eaten them before. But she won't eat them
now in case the dogs next door have widdled on them, apparently.