Adding baggage during a stopover...
 

Hi all,
I'm flying OSL to LHR on a Monday, staying in London Monday to Friday then flying LHR to SYD via SIN on Friday. All booked through QF. I will only have one bag OSL to LHR, but two bags LHR to SYD. Are they fine with you checking in another bag? I assume I can take my one bag as I'll need it while in London, but when I go back I will have two bags to check in.
Hope that makes sense!
Thanks

Not a problem, you have a stop over not a transit (you can also checkin luggage on a transit). Your bags will be checked in by BA in OSL to LHR, then 5 days later you rock up to LHR and QF will check in your two bags - and apply any excess luggage if you are above the limit for example.

there is no option that your bags would have been checked in to SYD and stored at LHR for five days….