I agree with what has been posted above. Thatcherism wasn’t some sort of bolt from the blue. You can’t bring in a solution until the problem is manifest. 95% of people in the fifties and early sixties were quite content with the overall structuring of the economy and saw no reason for radical change.
I would posit that part of the problem, if you want to define it as that, was that the electoral/economic cycles never brought themselves into a position where the climate was conducive to reform. By the time Labour took over in ‘64 the problems were becoming more evident, but Labour, for obvious reasons, was never committed to real reform. When Heath took over, it was all too easy to utter platitudes about stabilising the economy and making slight reforms, on the back of Labour’s extremely mixed record. All those big Heath ministers had had their heyday under Macmillan. They remembered that long stretch of government under One-Nation economics and naturally in the main they reached for all the familiar levers and toggles with regard to policy.
It is hard to decide how things would have been effected if the Conservative Party had had more mixed electoral fortunes; Labour’s economic record in the 1945-51 period did not provoke a strong response against the fundamentals. All that was envisaged was a return to ‘sunlit uplands’, I.E, getting off austerity. The position of the party electorally was still extremely weak in the early fifties (What was the Tory majority after ‘51? Twenty?) and consequently there was no real appetite for radicalism. ROBOT-style schemes were feared because, horror of horrors, they might produce a temporary rise in unemployment, with an expected serious electoral knock-on. As Full Employment was the top deity in the Butskillite pantheon, anything which was perceived to aggravate it, how slightly and for however short a period and for whatever sort of long-term economic advantage, was more or less automatically deemed to be deeply wrong in the fifties.
Really, though, it depends on what you consider to be the strongest features of Thatcherism. Monetarism itself encompasses a range of economic tenets and was a reasonably small part of the overall package. I would argue that privatisation and trade union reform were actually more salient, and politically decisive features than monetarism. And both of those were much more likely to be adopted by the Tories in the ‘45-’79 period. Privatisation actually was, it was just incredibly limited, and was, in the most prominent case of iron and steel, reversed by Labour. Trade Union reform was also being raised by the mid sixties, but despite the Heath government’s dalliances with it, it was never properly implemented because of the immense obstacles. (Namely, the unions still thought they should be allowed to do whatever the hell they wanted, and people still had a tolerance for it.)
Unless you have a politically prehistoric POD, I don’t think you can get Thatcherism in the fifties. At all. The earliest, I think, you could contrive something even vaguely like Thatcherism with a post-war POD would be the mid-to-late sixties. But you would have to be very creative.
So not sure really. Having the Conservatives lose in ‘59, or thereabouts, might be an interesting one. How about trying to wrangle Peter Thorneycroft into the leadership?