According to Qantas web site for benefits of Qantas Club membership:
Dedicated check-in
To help avoid queues, members may use The Qantas Club priority check-in areas available at most airports. If there is no dedicated Qantas Club check-in, you may check in at the Business Class counter prior to any Qantas flight, regardless of your fare class. You must be travelling on a Qantas operated service with a Qantas flight number. If only carrying hand luggage, and travelling on a Qantas* or Jetstar marketed and operated flight, you can also check in at any major domestic Australian or New Zealand Qantas Club lounge.
There is no mention here of domestic or Australian airports only. It does mention that it must be a QF flight number and QF operate flight. So QF10, QF32 and QF2 out of LHR should qualify under that definition. If I was a QP member I would walking up to the Business Class desk to check-in and would be a little miffed if denied.