That was almost perfect! I had to add another ';' after the '0' to end the layer command. I hadn't thought of invoking it on the command line, so thanks very much!
^c^c-purge;a;;n;audit;y;z;a;-LAYER;SET;0;;qsave;close;
p.s.
I hope this little command string proves useful to other users as well. Maintaining a clean drawing not only makes life easier but it keeps file sizes down and maintains consistent views and settings. Rolling it all into one command string also makes it a one click command and should help even the laziest of draughtsmen!