Are you aware of the current problems at Avanti? They operation has descended into chaos. They have introduced a reduced timetable, and (from your perspective) the good thing about that is that the reliability on the Liverpool route seems to have picked up, but it is by no means what you'd call acceptable. (A few months ago the cancellation rate on the Liverpool route was dreadful).
You're aware that only the late evening departures from Liverpool stop at Watford Junctions. Services departing Liverpool before 1700 don't stop.