Thanks guys for the prompt responses, played around some more and got it sorted.
The assemblies I was selecting were on different layers, so the attributes dialogue box doesn't show.
If all the parts of the assembly areon the same layer, then the attributes dialogue does show, and the layer can be changed.
Of course, the reason I was selecting the assembly was to get all the parts on the same layer - just what I cannot do.
Any suggestions on easily getting multiple entities on multiple layers onto one layer ?
My approach will be to turn all layers off, then select the layers one at a time and move the required entities to the desired layer, not really a drama at all.
look into Options -> Application Preferences, in the Defaults tab you find the option "Modify layer of selected entities, at layer activation".
When this option is checked, all selected entities are moved to the layer you select in the layer list, no matter on which layer they were before.
As this feature was annoying for some users when it was released, it is disabled by default. This feature could also be dangerous, maybe it is better disabled in daily work and only activated when really needed.
investing less than half an hour into Search function can save hours or days of waiting for a solution
Thanks for that.
At my stage of learning, entering into something labelled as dangerous by others doesn't sound wise.
My work-around will be adequate for now, but your advice is noted for the future.