it was nowhere near as complex as DLS (BTW RIP Dr. Anthony Lewis MBE)
League points per game is the normal method used to decide best playing record when on league is missing a side and you need to decide which team gets to play at home in the play off.
However, as some sides had more home games to play than others, they actually took the average league points gained at home and awarded that for any remaining home games and did the same for any remaining away games.
I am no sure if this actually made any difference over simple PPG - I know it didn't in the national leagues, I just have not looked below that.
But it does seem to be about the best possible solution.