Molto thanks to tjh in the CB for the solution to this problem (and shame on me for not reading the manual finely enough) - the answer is to create the new ftp object with Passive mode turned on,

my $ftp = Net::FTP->new("ftp.xxxxxxxxxx.xxx", Passive => 1, Debug => 1
+);
[download]

So that's fixed. Although I'm still puzzled why one needs to do something different in order to call the script in a different way...

§ George Sherston