If the journey is on a single ticket/single fare, then APD will apply as normal. Buying two tickets at seperate fares will avoid longhaul APD but will be more expensive and will not guarantee connections
I sit corrected. Having almost never connected from the UK to longhaul via a european hub, I was incorrectly assuming that if you flew, for example, MSE-AMS-HKG that you would only pay APD on the MSE-AMS bit.
Anyway, wish MSE luck with getting this off the ground.