Morrisons is situated in Holloway Road, at the beginning of The Enemy, residents of the Morrisons group are at war with the group that live at Waitrose from across the road, although they later join forces to travel to Buckingham Palace together.
The only time Morrisons is properly seen is during The Fear when Jester tries to get inside for protection from a group of sickos but gets rejected and he instead goes to Waitrose, as seen in The Enemy.
Not much is known how the Morrisons group are set up in the store but it is assumed that it is drastically different from how Waitrose are set up.