Ok, here goes.
In 1930, Mosley defects from Labour and founds the New Party. Amongst those who leave Labour and join the party are Nye Bevan(Which almost happened in otl) and Harold Macmillan.
The platform of the New Party develops into a policy of Britain first, Empire second( which is an otl buf slogan, but they shys away from the otl part of the slogan foreigners nowhere.) The New Party claims that Britain is on the decline and that a radical solution is required. They argue for the creation of the corporate state along lines similar to Italy, but it is stressed that Britain would remain a democratic state.
The party gains the support of the Daily Mail, the Daily Mirror and other papers who see the party as a bulwork against socialism. They stay away from the blackshirt tradition. The Party does not become anti-semitic. From the background of the increased funding, the New Party gains 15 Members of Parliament at the 1931 General Election.
During the period of 1931-35 the Party concentrates on building its profile and support amongst both the Tory working class, who they argue their policies will help secure them more influence without socialism, and the middle class, stroking up fears of the red terror. They openly critisise the excesses of the Nazi regime in Germany.
In 1933 they rename themselves the British Union of Fascists. In 1934, a uniform is developed for members which is similar to the uniform of the British Army.
In 1935, there is a Sterling Crash, the General Election is postponed for another year. In the 1936 General Election, the BUF gain 100 MPs in a Parliament dominated by the Conservative-led National Government. Labour finish third, and Mosley becomes the leader of the opposition.
Thats as far as I can go. I cant see Mosley becoming PM.