I thin the fact they are announcing that Todays episode Declan Napier will be played by Ern Mullaney sums it up, without that we would be all lost as to who on earth this weird greasy fella holding india was meant to be.
They announced it at the beginning when that other actress played Libby too, so it's something Neighbours normally does when another actor takes over a part. I think it's quite a good idea.