Just to re-cap, To support texture packer I will do the following…
1 - I will create a tile set using “collection of images” tile set type
from a working assets directory containing images/animations.
Tiled will create a TMX file containing tile assets like:
<image source="../../../texturepacker/collectables/coin.png" width="32" height="32"/>
2 - I will use texture packer to pack that same directory, it will
create entries that map to the texture packer sprite sheet as:
<SubTexture name="collectables/coin" x="2" y="2" width="32" height="32"/>
3 - I will load and parse the TMX file in my custom game engine, and parse the trailing image source starting at /texturepacker which leaves me with path :
collectables/coin.png
This is the key I will use to lookup the sprite sheet atlas - trimming “.png”.
Help this helps @T1mL3arn, Thanks again @bjorn.
btw - What could be a cool feature is to be able to add smart directories to a tile set in the same way texture packer does, I.e. listen to local file changes and dynamically add new files/folders etc… obviously a different topic 
.