Hello there!
A slightly more helpful answer I hope: The second of the motivation papers is slightly more difficult and does tend to test the details given in the document - including frequencies. It also requires you to answer some more mathematical problems. It is similar in length to the initial. Best advice, just learn the ENTIRE document. You'll need to know it at some point anyway!
The HR interview isn't too bad. It's an hour long with a member of the HR team. They don't smile, don't really react to anything you tell them. They merely have a bunch of questions and a list of possible answers. They'll stop you once they have got an answer that is similar to yours.
The computer tests are hellish! Can't really describe them without enducing a hell of a lot of fear on your part. They're horrible, but manageable. Just prioritise and don't let it stress you out too much! It's around 30-60 mins long and you can take all the time you want. Also, you can practice before hand. I'd recommend making sure you know exactly what you're doing before moving on to the actual thing! lol.
Hope this helps, Ricky.