When I worked down the pit, in 1980 I recall the coal face / heading rate, (basic pay) was £150.00 per week (five shifts, without bonus or overtime.) This top rate was called power loading agreement or PLA. With overtime & bonus, you could make a good living by most people's view of a good living.
Obviously, things had moved on since Byker Hill was written!
Just to clarify an overman. the overman was the management person responsible for an area, say a coal face, for production. The deputy was the management person responsible for safety of the team.
I was an electrician, so my mates thought we were responsible for sleeping.....
Pit meant deep mine as far as we were concerned. Mind you, terms change over a short distance. For instance, when I was an apprentice at college and area workshops, we were told the "trains" were called paddys. At my pit, we called them... eerrr trains.
This was Yorkshire / Nottinghamshire border area.