The 16 June 1974 TV preview says it will be shown on Tuesdays, but all the Tuesday papers that are available to view just say "To be Scheduled" in that 8.15pm slot. It's unusual that JBC didn't know what they were playing in that slot for weeks on end, especially if it was a regular weekly series like DOOMWATCH.
From 6 August, "Colditz" is actually listed in that slot. From the dates, no more than 8 eps of DOOMWATCH could have aired. As it so happens 8 is how many episodes of Season 1 that currently exist! Read into that what you will...
It's a shame that no one appears to have access or records of the BBC's Retention Authorisation Sheets or access to overseas sales information that might shed some light on the worldwide distribution of the series. A summary of what is known appears here
If anyone can find actual listings for DOOMWATCH from 1974 onwards on JBC, of which there seems to be none please get in touch.
With thanks to Jon Preddle