Late reply to this but I was told after taking theory test by one of the test centre folks that it is not the amount of times you press, it is if the system detects a pattern. If this is true then pressing every 2.5 seconds would set off it's "anti pattern" thing. I'm not saying this is true but it is what I was told after my test (which I passed). Just thought I would say as there do seemto be a few rumours about the hazard perception part of the test.