I did it last month - ie transferred mobile only from Orange to Free. It all went very easily but I did not get the bank confirmation thingy, just a snail mail form I filled out and sent off to Free authorising direct debit (and my guess is they activated the SIM before they got this as I was a bit late in posting).
I was transferring my old number across and it took about a week to activate but all went quite smoothly. If it makes any sense, another Aussie in the village signed up at the same time but was getting a new SIM and not transferring an old number. She did have to do the bank verification thing (same bank as me). Different process doesn't make any sense to me but may to someone else
Steve