Step two above is exactly what I wanted but I wasn't quite sure exactly what was required but I am now so for others for future reference:

   # use proxy (comment out if not)
   my %proxy = ( host => 'http://proxy:8080' );

   use LWP::Simple qw(mirror RC_OK RC_NOT_MODIFIED $ua);

   $ua->proxy(http => "$proxy{host}") if (defined $proxy{host});
[download]

You can see I'm just interested in using mirror.