It helped me pass first time!
I passed my theory test first time using the disk. The questions were in exactly the same format as on the actual test which was really helpful as I knew what to expect. There's loads of questions and you have the option to revise, practice and take mock tests whenever you like.
The hazard perception disk was also really helpful as it taught me when you need to click in order to score which can be a bit confusing. This disk is basically just a DVD when a women talks to you about potential hazards. I didn't watch all of this and skipped to the practice video but still managed to pass this easily. I was slightly disappointed that there was only 10 practice clips on the DVD, I expected at least 14 as there's 14 on the actual test which was the only downside. However there's plently of practice videos if you do a search online.