I tend to agree with you CrackedAxe, those units you saw were Hun Nobles and Hun Horse Archers. The Alan mercenary horse archers were basically the same as the Hun HA apart from the saddle cloth, yes? Other units such as Gepid infantry and Visigoth cav were very similar to units we have already.
I would not expect the Hun units to be created for just one TV episode.

The armies that clashed that day were extremely similar in construction and in fact, Aetius was a great friend of the Huns and Attila until this battle. The Huns had made up the majority of his western empire armies that had been surpressing the revolts in Gaul and fighting the Visigoths, the truth has become a little forgotten where the Huns are concerned. The Huns had caused no end of trouble for the eastern empire but even when they had the opportunity, they did not overthrow it. The reason was simple, the Huns needed the eastern empire and by overthrowing it would have severed a valuable source of income, whether by tribute or looting, such was the nature of Hun society. They did not have the resources to run a complex society and lived by predation.

But talking of the armies of those times, they were all very similar and were even constructed of the same peoples, many 'Roman' generals were Visigoth and there was at least one Vandal that I can recall. Likewise, Attila had a Roman among his senior commanders. Add to this two Frankish brothers in a hereditary dispute who sought help through opposite avenues ( one went to the Huns, the other to the Romans ) The armies of the area were Roman, Hun, Visigoth mainly by name only.

Hopefully you are right about the expansion, the Huns get my vote

......Orda