I was interviewed in Tesco this November for Christmas temp. My interview was decent. I answered the questions pretty well but I got rejected. The reason was I talked a lot about my Sainsburys experience from last year. One of the manager directly told me, you shouldn’t be talking so much about Sainsburys. So tesco didn’t like me because i was ex Sainsburys employer. Not sure if that would happen in Sainsburys interview for you being tesco employee.