Originally Posted by
jansoncheng
...Therefore, it all depend on the CX ground crew in JFK, In best case, they will help you to get the JFK-HKG and HKG-LHR boarding pass and checked your luggage to LHR. But in worst case, they may simply rejected your request and you need figure out how to get your luggage out in HKG.
As suggested earlier: Courier your luggage home. Even with being checked in, you can walk out at HKG.