I've nothing going back to 1909, but in 1933 (my earliest Broadcaster Trade Annual) Glasgow Corporation was supplying a mixture of AC and DC, both at 250 volts. Also mentioned, and unique to Glasgow, is a 6500 volt DC supply, presumably for some specialised application rather than for certain bold or unfortunate householders.
There's much background information at
https://www.gracesguide.co.uk/Electr...he_early_years .
Paul