Alright Branden,
I might be able to give you a bit of an insight although when I went to see them it wasn't an assessment day just an interview.
Basically it consisted of an interview with a couple of young lads (bearing in mind i'm only 22) and then a series of tests. The test were mental arithmetic, pattern recognition and a paper with numerical questions on, now I had absolutely no idea what the questions were on the last paper or how to answer them. Needless to say I didn't get called back for a second interview
Mike