Copying from one instrument to another

Hi, I am working on a musical and have to change and transpose the violin score to be played on a cello. I have tried adding an instrument(viocello) and part, then select everything from the violin score to be pasted to the cello part (to be transposed down one full octave). This kind of works but all the pasted notes appear at the same line and space and as the cello score is in bass clef they are all too high by one full tone.

What am I doing wrong? Is there a more elegant way of copying an entire instrument?

Many thanks in advance!