The reasons British hockey was so high scoring in that period are basically:
Teams had basically amateur players with 3 imports, who were the teams best players. They were normally 2 forwards and one defenceman (who played 55-60 minutes). Import goalies were very rare (and of course hockey in Britain was and is played with 1 goalie, 2 defencemen and 3 forwards).
Most of the good British players were concentrated on very few teams (Durham, Murrayfield, Dundee), and other northern and scottish clubs.
Teams didn't play defence at all.
Teams normally played 2-line hockey, so there were plenty of tired players making mistakes.
It was a very physical league, so there were lots of powerplays.
Like all leagues British hockey swung from def
That's basically it. Here's a picture of a game of hockey from Britain in the 60's played at Durham. At the time the rink was covered with a marquee, hence the pole in the middle of the ice:
