According to The National Churchill Museum he said
"Those who can win a war well can rarely make a good peace, and those who could make a good peace would never have won the war."
1930, from his book My Early Life.
Which doesn't mean exactly the same thing but has a similar sentiment.
In a speech in Parliament he also said, Of his predecessor Chamberlain who made the notorious Munich Agreement with Hitler and subsequently announced "peace for our time"
Whatever else history may or may not say about these terrible, tremendous years, we can be sure that Neville Chamberlain acted with perfect sincerity according to his lights and strove to the utmost of his capacity and authority, which were powerful, to save the world from the awful, devastating struggle in which we are now engaged. This alone will stand him in good stead as far as what is called the verdict of history is concerned.
So it may be that Churchill's views on peacemakers were markedly different from what you might understand from the Spanish phrase.