The official LNAT practice questions are harder and more realistic than the guides, so it’s normal to score lower on the LNAT website.
A jump from 30 on a guide to 12 on the official site doesn’t mean you’re suddenly worse, it just means the official questions are tougher, denser and stricter with timing.
The best thing you can do now is focus only on official LNAT practice,
because you've seen now using soley the guides to practice won't help you much if you want to achieve signficiantly higher than 12, especially working under full timed conditions.
Don’t worry about the score difference too much; lots of people see a big drop when they switch to the real-style questions but improve quickly once they get used to them.
Practice reading actively, skim for structure, and don’t get stuck on tricky passages, always keep pace.
You still have time to tighten your technique, and your score can move a lot with a few days of consistent, timed practice.
Hope this helps,
Ulaw,
Alfred.