Getting this thread slightly back on track...

Thanks to everyone who's replied and helped bring Tagret Sector out of the shadows, I'm still not sure though that it was what I remember reading, I could have sworn it was an actual published sector rather than a magazine insert, but it would be interesting to see what a further search would turn up.

The following also interests me,

"I also always wondered about Grenadier Miniatures Aramanth subsector, which from the description on the back cover of their adventure was a sector or two Coreward from the Imperium's coreward edge... Somewhere in the Vargr Extents???"  (Frank)

Did Grenadier include a subsector map with their publication or was it just the adventure setting?