This is the common mushroom you find in shops: the white and chestnut buttons are harvested before the cap expands, while Portobello mushrooms are taken when fully grown. There are surprisingly few records for this species in the wild for Scotland. Almost certainly under-recorded as the spores must be in bought compost and on compost heaps.

References: 
Kibby, G. (2011 third edition). The Genus Agaricus in Britain.
Læssøe, T. & Petersen, J.H. (2019). Fungi of Temperate Europe, Volume 1.
Sanchez, L.A.P. (2008). Fungi Europaei, 1: Agaricus.