Restaurants in the UK where I live, want to put things right on the day. They depend on repeat business. They would rather change a meal and keep their regular customers, than have people smile and pretend all is well, then never dine there again.
So, yes, I will politely sort out a problem with the restaurant, there and then. I want to keep the standard high and return again. On the rare occasions I have asked for something to be re-done, the waiters have been fantastic.
Sometimes a free drink is given for the inconvenience. But then England is such a civilised country - civilized to you lot.