Hi Malcolm,
I cant answer your first question on sound quality but your second point regarding them only being in mono vs stereo is quite easy to guess why.
These long haired working class rock and roll yobs were not quite held in the same regard as they are today, same goes for most recording artists of the time who played the 'Devils Music'.
The fact they were recorded at all is a miracle let alone them only having the simplest 4 track mono equipment to record with at their disposal.