Who do you have an agreement with? Deutsche BA fly to HKI from Munich and Berlin I think. BA from LHR to HKI. If you want to have a fun journey, try Ryanair to Skavsta ("Stockholm" South) and catch a ferry across! Sure to meet some girls on the crossing! Alternatively, if you get concessions with Estonian, they fly from LGW to Tallinn, and you can catch a ferry from there to HKI.
DB