Thanks for the reply.
My last.fm account is already configured with MC & works fine. All tracks I play directly from MC get scrobbled / logged to my last.fm page successfully, so I don't think that's the issue.
I don't believe I currently use JRemote features at all.
What I would like to happen is that if I use my iPod while I'm out & listen to say, 30 songs on it, when I get home I can plug the iPod into my PC with MC running and re-sync the iPod so that it reports my new iPod plays to last.fm.
Currently MC can see my iPod fine when it's connected, under Standard View > Devices
It automatically registers (syncs) new plays on the iPod and updates the library, so that the Last Played Date for the songs I've listened to on the iPod whilst out is reflected in the library itself.
What isn't happening is that the new plays from the iPod, although being logged to the library, aren't then reported on to my last.fm account as new plays (as a track played directly by MC would be). So although the MC knows about the plays, it doesn't share the information with last.fm.