Right, I appear to have solved the problem, neither of which were Flirc's fault.
Basically the remote was originally shipped using a reprogrammable 4-digit code system, later they shipped an identical remote which required only 3 numbers, differentiated only by a small white label inside the battery bay....see this thread: http://myhumax.org/forum/topic/remote-control-confused-if-3-or-4-digit-codes#post-235
I'd chanced upon the 3 digit codes and was trying to use those...needless to say Flirc responded with the errors mentioned above.
My only problem now is trying to find a 4 digit code that uses ALL the buttons of the XBMC profile in Flirc's config. I had one that did all buttons except FF, for now I'm using one that uses all buttons except volume up, down and mute (handled by another remote anyway).
Enjoying my Flirc now, thanks Chris!
Hopefully this will help anyone else...not all remotes are the same, even when they are!