Hi @alastair_leith ,

>>>>Right clicking the OLD_BLOCK listing in the Blocks palette doesn't let me delete its nor do any palette menu options.

If you mean blocks listing on the "Blocks in current drawing" tab of the Blocks Palette, then - yes, you cannot delete unused block here.

You can remove unused block definition from the drawing only with PURGE command. If you cannot remove it, then you can check why you cannot do this on the "Non Purgeable Items" tab of the Purge window:

 >>>>I can't use the BLOCK text command,

Command line version of BLOCK command is -BLOCK