First step was a standard online application followed by tests and a request for a phone interview. This was the shorted phone interview I have ever had and I didn't think it has gone very well. Be prepared for the logic question at the end - I wasn't and just babbled on but at least used some structure even though I worked it through properly afterwards and was 100 miles off the real answer.
After 4 weeks (a lot longer than I was told it would take...which becomes a theme) I was told I passed and could I attend an assessment centre. This day was standard and has been described below: presentation on DH, we present to two assessors on some Tesco data you have an hour and a bit to analyse, interview (very easy competency based) and finally a group discussion.
After this I waited about a month and a half to hear back after being told it would take just over a week. Didn't get the job but the amount of time it took to get back to me was my only complaint. Very pleasant (albeit disorganised) application process and a very interesting and innovative company, which I would recommend applying for!