Being charged for return when the size is really off.

[DublinDoris2000]

I've just bought two pairs of shoes from Boden, both size 41, this is my size 95% of the time, I find EU sizing much more reliable.
One pair fit great, the other are at least a full size too small.
Returns are €15. I don't think its fair to charge me for a return when their sizing is so off. I would keep the shoes if they fit.
What do you reckon my chances of arguing this are?

Can you return them as faulty, take photos with a tape measure and comparing them to a genuine 41 size shoe, state they must be mislabels and request a free return as faulty.

that’s what I would do anyway.

I would request a faulty return too. It’s done you a favour buying two pairs of shoes the same size at a the same time, because they can’t reasonably argue that both are the right size when only one pair fits