Completed stage 2 around a month ago, Didn't purchase any symbiotics assessments (seemed very expensive) or CAE material and in all honesty did very little preparation, it wasn't particularly challenging. What drained me the most was the FAST multi tasking exercise at the end.
Personality tests were as expected, I've answered questions like that hundreds of times before, nothing out of the ordinary.
Got an email the next day inviting me to stage 3. Completed that recently, thankfully all my preparation paid off and I received an email informing me I had been offered a place on the MPL course.