There's a reason that properly refillable bottles are available at a cost; this cost is also the reason why someone will always come up with an adapter to make something do what it shouldn't (or that we shouldn't do with it anyway!!) Having used badly refilled bottles in Spain, every town has somewhere that will will refill just about any bottle, I am accutely aware of the potential for leaks etc.
Looking at gas prices locally it costs me under a tenner extra to get a proper exchange Propane bottle rather than fill mine again from a pump so it would be four refills to recoup the cost of the adapter (or about eighteen to recover the cost of a proper refillable bottle). I'm usually pretty tight with my money but on this one I'm happy to pay the extra and keep getting genuine swapped bottles, if only to keep my insurance valid in case of a gas explosion....

Andi