good to see those photos
of the burco Mike, it must be quite unusual to have a spin timer rather than a wash timer. Again as you've said, I don't remember people using the heaters, maybe by my time in the 70's the fuel price rises, people weren't into boiling as much, and as hot water was available from back boilers or immersion heaters, once the machine was out, most would just want to get on with the wash. I remember one lady telling me her routine was to come back from the shops, put the tank on, then fill the machine and do the wash. Perhaps we would have filled, added detergent and whites, set the heater and timer and return to continue the wash, better results and use less electric than heating a whole tank.
But back to the spin timer, did anyone actually run the spinner for 4 mins, again I remember most running until the last drops stopped pumping and get them on the line. Maybe in the wet weather things got a longer spin. but again I would think the wash timer would be more useful.