The problem with generalisations is that they are just that and while I can agree with some of Francis King's comments I would certainly object to the conclusion that the Soviet model was "marginal" in Labour thinking -- though perhaps for differing reasons.
I won't rehearse the reason for the adoption of Clause Four after the 1917 Revolution because I assume we are all acquainted with it and for the reason why the two McDonald Labour governments failed to introduce any meaningful social reforms in the 1920s.
The key issue Francis raises is the drive to create welfare states, public sectors and "safety net" social legislation in the immediate post-war period in Britain and the rest of Western Europe and the further development of the state sector during the Wilson-Callaghan government in the 1970s.
The Attlee government's sweeping social reforms came, as Francis implies, from a bourgeois consensus that working class demands had to be met in some way and that the only way the essentially capitalist state could be modernised was with the help of a major subsidised state sector. Clearly the European bourgeoisie were concerned at the growth of the communist movement in France and Italy following the establishment of people's power in Czechoslovakia in 1948. They were also concerned at the influence (directly and indirectly) amongst left social-democrats in an era when the Trotskyist movement was irrelevant and minute.
In those early Cold War days (and indeed when I was at school in the 1960s) Labour's dogma was that social democracy sought to nationalise or direct the means of distribution but not of production. The Soviet Union and the people's democracies were routinely described as "totalitarian" or "police" states and unfavourably compared with the so-called liberties that British workers were told they enjoyed. At the same time Labour also claimed, with some justification, that the National Health Service was superior to the Soviet health system because prescriptions were set at a nominal level (and for a very short period entirely free).
The other issue is the question of Labour's concept of social-democracy and whether it represents a distinct ideology as opposed to simply being a version of Keynesian economics. Wilson simply called it "pragmatism" -- anti-communist Labour politicians like Richard Crossman and Tony Crosland wrote books extolling what they claimed was a superior way of administering capitalism to produce social justice.
But what was this "pragmatism" in practice? I suppose the key word was "partnership" or "tripartitism" brought to finesse with the corporatist "In Place of Strife" plan that was moved by the first Wilson government that was rejected by the TUC and the later swathe of bodies set up by Labour in the 1970s. While none of this was inspired by Stalin you could argue that much of this thinking (tripartite committees,Health & Safety legislation, facility time for unions, National Intervention Board, National Economic Development Council and so on) owed much to Mussolini's Italy. While I'm not seriously suggesting any conscious imitation of fascist models there is an echo of the "Mondism" (class collaboration) that the right-wing of the TUC bought into during the 1930s.
Throughout this period senior Labour politicians would constantly stress the supposed superiority over the Soviet model -- if it was raised and the one exception was comprehensive schooling which was diametrically opposed to the Soviet system of rigid streaming.
Eton & Cambridge