Connecting flights with different airlines - DUB > LA

[SydneyFly]

Hi AFF,

I've booked a flight from Dublin to LAX via Skiddoo. The first leg is flying British Airways while the second leg is via Virgin Atlantic.

[TABLE="width: 598"]
[TR]
[TD="colspan: 3"]Flight Details as follow:[/TD]
[/TR]
[TR]
[TD]FLIGHT[/TD]
[TD]DEPART/ARRIVE[/TD]
[TD]AIRPORT[/TD]
[/TR]
[TR]
[TD]BA827[/TD]
[TD]THURS 11:40AM
THURS 1:10PM[/TD]
[TD]DUBLIN (DUB)
LONDON (LHR)[/TD]
[/TR]
[TR]
[TD]VS23[/TD]
[TD]THURS 3:45PM
THURS 6:55PM[/TD]
[TD]LONDON (LHR)
LOS ANGELES (LAX)[/TD]
[/TR]
[/TABLE]

I'm a bit lost on how my baggage transfer and checkin will work. Will I need to check into both flights from Dublin? Will the airlines automatically transfer my luggage to the connecting flight? Do I ever need to exit the terminal and re-enter immigration/security?

Any help and advice will be greatly appreciated. I'm Qantas Gold if that helps.

Thanks!