I applied online. I interviewed at Matrix Education in Dec 2018
Interview
Fairly relaxed interview.
A head tutor (or more than one) will interview you asking about your education and motivations.
They will then give you a couple of maths problems and role-play a student who is requires help with these questions.
Interview questions [1]
Question 1
Various math topics across the high school syllabus - I had a fractions question and a curve sketching/calculus question
I applied online. The process took 2 weeks. I interviewed at Matrix Education
Interview
They asked questions. There was a lot of getting to know each other and then they got me to demonstrate how I would teach a question. It was pretty relaxed.