What seems to have happened in practice, at least in some places, is that if there was no reply, the register was left as it was, names were not removed.
The dates were changed at some point, at least by the 1970s. The information was collected in October. The draft register was made available in December, in libraries as well as post offices, and the register came into force on 1 February for 12 months.
It was around 2001 when privacy concerns closed public inspection of the draft and current registers. An appointment was needed to check your own entry. However registers prior to the current year seem to be available in libraries.