I worked at Tesco as a contractor (Less than a year)
Good tech stack and location
No much cons to talk
I applied online. The process took 2 weeks. I interviewed at Tesco (London, England) in January 2016.
Codility then face to face with system design questions, coding exercise, char with hr. The office in London looks more like a startup which is fine for people who like that environment. I didn't like the location.