Well I'm not blowing my own trumpet here but after doing very little preparation for the cubes I answered them all and got through stage 1. As many people have said, over practice and you're just kidding yourself, if you have practiced for hours for a 20 minute test, how long are you going to have to spend extra if you get through and go onto training?
I think it is important to know whats ahead of you but unlike GCSEs and A levels you're not working against a set curriculum as such and therefore it should be treat like that. I'm not saying don't prepare but hours and hours of practice may get you past stage one but its your time you're wasting when you don't get past S2, S3, training or validation.
All in all if NATS wanted you to practice, they would let you do so on the SHL website or their own.
You owe it to yourself to relax, get a good nights sleep and a good breakfast, and thats it! Thats certainly the mindset I'm taking in with me to S2 anyway!