First a thanks to owenr, your instructions eventually got me to the required result. Unfortunately I saved the file WITHOUT the history and couldn't repeat the steps on my main wireframe file !
My problem is the creation of the 'vector rectangle', then the mask from the vector shape and the rectangle. When I go to do the Boolean subtract the only option in the Geometry is 'divide', all the rest are greyed out.
Watching the videos on masks I seem to be missing a piece of knowledge as to the difference between creating a vector and a normal image mask.
Also is there an easy way to select the whole of the large bear and use it to make the mask, then I could put multiple small bears behind ?