Isn't just that a woman can do it FOC but a man has to pay? Or did I hear that wrong? Not that it would be a strong enough deterrent for a couple wanting to do it that way, but if it's correct it's a baked in aspect of patriarchy.
I believe that either spouse can choose to take the surname of the other for free, but not create a new name or a blended one without paying for a deed poll (£42.44)
Just to point out that either partner can change their name when they marry.
P.P.S. Fuck the Tories