This is accessing the USB drive/FTP server from the internet so its not via the second WAN link on the router, purely via the ADSL line. I have tried to do a raw telnet on port 21 externally and I cant connect. But if I forward the port to a workstation running as an ftp server I connect fine. I can connect to the ftp on the Draytek from inside the LAN fine.

Thanks

You need to enable management from the Internet (under System Maintenance then Management) and on there enable the FTP server. Once that's all enabled and you've got some USB user accounts, you should be able to log in to the router's FTP server using those accuonts to access the USB disk.

Is there anyway - apart from changing the management ports I can enable ftp but disable the SSH/HTTP/HTTPS etc as when we enable the ftp which enables the remote management is stops traffic going through to our server for OWA services etc?

Thanks

The router will usually reserve those ports anyway so it's always worth changing the management ports if you've got servers that would need to use those ports on the WAN side. You would need to change those ports to get working in that way but leave unwanted management options such as HTTP remote management unticked.