LHR QR lounge allows J/F passengers, right?
No, for two reasons:
1. oneworld lounge access is only available when you are departing on a oneworld airline.
2. The QR Premium Lounge at LHR is excluded from oneworld access anyway.
See:
http://www.oneworld.com/ffp/lounge-access
Since we're traveling in J/F, (2) does not apply. But since Jet is not a Oneworld airline, (1) does