Surely the thing to do is tell everyone that you're flying to somewhere up country, then declare a fake problem and divert to an alternate close at hand when you enter UK airspace. While C&E are still waiting for you at Aberdeen or wherever, dump contraband and vanish into night. You'll need a friend airside, but apart from that no-one need know your true intention.
Honestly... have these people no imagination? It's not called dope for nothing, I guess.
A Friend Of A Friend used to pay for his flying, electronics hobby and drug habit by pootling over to Holland in the club's Centurion, picking up a few kilos of goodies, slapping a radio beacon on them and throwing them overboard when he came home over Epping Forest. He'd pop back on his bike the next day and track the packages down. Eventually he got sloppy, spotted and nicked, in that order... but I'd be surprised if multiple similar scams aren't going on all the time.
R