So after going round in circles with this for the best part of an hour my iPod classic is now syncing. I have no idea what solved it. But here are some of the things I did.
With the iPod disconnected, restart the macbook (i've an oldish macbook pro i7 processor)
Log in to the mac
Hard restart the iPod (hold menu and ok button for over 8 seconds)
Plug the iPod into the mac
Open finder and click the icon of the iPod - this then gave the option of syncing.
Immediately before this I had a message in music that I needed to use finder to start using the iPod
So I went to finder, and there was a notification to start using the iPod, but everything just froze (which is when I did the above)
Before this, I went through blowing on the usb connections, restarting the mac (lots of times)
I was lucky that when I first plugged the iPod in, it asked me if I wanted to restore the iPod.
Hopefully it will continue to sync.