So, very sadly, pretty much as surmised earlier - a poor plan with inadequate met appreciation and a pilot's ambition exceeding his ability to manage the flight.
The self-imposed pressures to get the family to Ireland seem to have clouded sensible judgement regarding both the preparation (over AUM on departure) and the conduct (ending up IMC on a VFR sortie) of this flight.
Another CFIT which could so easily have been avoided, RIP.