Checking through baggage (Virgin Australia to Singapore Airlines)

I have booked a Virgin Australia flight from MEL-PER to connect up with my singapore flight to london. If I were to take/book an additional bag, could I technically get away with just paying for an additional bag with VA (Not SQ) and hope they check through all the bags to london?

ps. I have rang VA and they said it is up to the discretion of the staff at the airport.

VA has an interline agreement with SQ for reservations using one Booking Reference. If you have 2 separate reservations eg, you booked directly with SQ for PER/LHR and booked directly with VA for MEL/PER, you can ask on check in at MEL if they can check your luggage through to London. Usually check in staff will do it. Suggest check in early at MEL to guarantee it.