Hi Eddie, sorry to hear that you have a problem with the effectiveness of your handbrake. This is not a flippant suggestion, get it back to your dealer and ask them to resolve for you.
In the meantime when you park up, stick it in gear to hold it.
I seem to remember when car began to get rear disc brakes, whose handbrakes were ineffective the advise was to apply the handbrake for the last smidgen of movement. just a thought.
As said above get it booked into your dealer.
