Originally Posted by britbronco22

Not if you haven't actually received any bonus miles for incurring the FX charges. I think you have missed the point here.
In a situation where you have to spend in a foreign currency, and you are deciding between a fee free card and the 10x Avios, I agree of course you choose the avios.
However I'm talking about the situation where you can choose to be charged in £ or FX (for example choosing between buying something at LHR or at your destination), if the price is the same you choose the £, unless you are actually getting extra points to cover the FX charge.