LearningAllTheTime
You say you have been to and read all of the NATS interview process thread.
If you had, you would have spotted confirmation (quite a few times) that the first online assessment is simply a very quick (5 minutes? It's been a while since I did it) basic checking test. Can you spot the difference in strings of letters and numbers?
You would also have seen that before you take the test, you're able to spend a bit of time doing practice tests, of the same format.
Good luck.