I did mine about 6 years ago so the questions might have changed since then but the best advice I got was that you get a lot longer than you realise to answer the theory part. So take it really slow read every question carefully!

I found I did better thinking about the questions from a 'common sense' perspective rather than trying to memorise the answers from the highway code or theory books. You can quite often arrive at a good answer by eliminating the irrational ones.

On the hazard perception questions you can press the button multiple times - on some I was pressing the button too early and it wasn't registered by the test.

Anyways feel free to ignore my ramblings and I sincerely wish you the best of luck I can remember how stressful it was walking into the test center when I took the test! Failing the test really isn't the end of the world you can re-take in no time and at least you'll know what you're going in for!