Hi Ted,
Thanks for the suggestions, but unfortunately I'm no further forward. As for an explanation, it's a bit tricky to explain because I really don't understand what's going on, and it's not like I'm new to this game.
Trying REFEDIT on the block doesn't display the attributes as being within the block. Likewise running ATTSYNC returns the following ...
ATTSYNC.PNG
However double clicking on the block brings up the the _EATTEDIT dialogue box ...
EATTEDIT.PNG
EATTEDIT - Text.PNG
EATTEDIT - Properties.PNG
I'm not sure if it's significant, but the block itself is inserted on a layer called BLDG.
Like I say, this has got me scratching my head. I know I could probably get around the issue by editing the text style, but that won't help me in the future ... Give a man a fish, blah, blah, blah ...