The UK Tories didn't 'lose their nerve' during the period after the landslide (I assume you're not asking us for speculation about something, anything, to occur before June, 1945).
What is that even meant to imply?
Churchill was an orthodox Opposition party leader, he ran a very loose, informally managed ship. There was no great emotional decision to make.
That's the thing: all the policy reforms and ideological changes, whether carried out by Butler at central office, or by the likes of MacMillan in the house, or even Cooper outside of Westminster, they all happened in a gradualist Conservative fashion.
Every notion of some great sellout is just revisionism from a later age.