I think we're back to debating what is and what is not socialism here, but the conflict was between labour unions and the state-owned enterprises that employed them. Both of which are very social democrat / mixed economy kind of institutions. Hence the Thatcherite response to both privatise everything (making employee relations someone else's problem, and also making it much easier to fire employees), severely restrict the unions, switch UK power generation away from domestic coal, and finally have a punchup between the police and the NUM.

The Labour party failed to develop any effective way of saying "no" to naked self-interest in unions (In Place Of Strife passim). Intrinsic problem in 'socialism'? Possibly.

That is a great quote on Attlee.