Who says there's a Perth base?
This discussion is all moot unless there's a base in Perth.
So far, I haven't read anything about a Perth base except conjecture here.
The only confirmed base at this point is Melbourne. Flights from Perth to London could certainly be crewed from Melbourne. With such a small initial fleet it doesn't make sense to start up a second base in the short term. In fact the costs of having a base in Perth would significantly outweigh the savings in accommodation in Perth.
Until the fleet numbers increase and the flying starts showing some statistics I find a Perth base to be unlikely.