I passed first time on Tue 4th Dec after having thoroughly practised on the official DSA iOS app. Scored full marks for questions and 77% for hazard perception.
I was really worried about the hp bit. Not because of missing the hazards and getting nil but rather clicking too early outside of the window and then being scared of clicking a few more times in case the program thought i was cheating...
As others have noted though, you can click 4/5 times in a row if it is during an actual developing hazard i.e. something that's gonna cause the car in the clip to brake or swerve. Clicking say 4 times when you're sure it's a developing hazard means you'll definitely click in the window and thus get a score.
While it's true that some hazards seem to appear and develop quicker than others, I don't believe that would prove to be detrimental to the overall score if you've been scoring well on the others.
I only used the 10 clips on the iOS app to practice with, again and again, to get a good idea how long the scoring window is and how soon it opens from when each developing hazard first comes into view.
I found the above advice very helpful which is why I am posting, to say thanks and to hopefully help someone else. I can recommend the following link too (apologies if it's already appeared somewhere here before).