OK, Mike and Gary, thanks for your patience with me and this dumb question.

The thing that particularly caused me to stumble was that when selecting a layer, the content is shown as selected by photoshop, but the actual size of the selection was not, so I was left wondering how big that selection was. My Doh! moment in particular was not using the selection tool specifically to select what was there and then have the actual size revealed.

It seems counter-intuitive to me that selecting a layer never reveals the size of the content on the layer ( unless I'm missing another trick ).

I did discover ( on my photoshop journey ), that selecting a layer, then duplicating it allows the layer to be duplicated into a completely new document or another open document, as-is so that's a great feature.

Generally as a new user I find photoshop quite clunky, but that's because I only use it for fairly simple things as part of a pipeline, rather than as an asset/art creator in it's own right.

Thanks Guys. Job done.