If you fail the HP, you shouldnt be on a bike, or outside of secure accomodation un-attended, in other words its a sinch !, you cant fail, its a test for dolphins thats been adapted (for a fee to the UK dept oT, from the USA, ok some format and script files have been changed, to suit the end user), but it pays £30 sterling into the revenue system, oh and costs you the aforementioned £30 sterling,,,,'
its an 'attendance fee', dont put any other thought to it,
as for the practical: keep your youthfull 'attitude-dude' switched off and view the 'old' guy (your examiner) as your kool uncle,just ride like a proper jessie for 40 mins, or something.