Just goes to show it's been a while since I set FTP up, I'd forgotten about that joy! 

As I mentioned I haven't tried FTPS but does that bring a particular complication over NAT? Aside from accepting passive connections over a narrow port range that has been forwarded through anyfirewall/NAT setup, is there more to it?

The advantage of FTP(S) is that the server doesn't have the capability to provide access to anything in the way the SSHd does, which means you're less reliant on locking down all the things the server can do but that you don't want it to allow.