IIRC Britain's last pre-war election was 1935, with Baldwin winning. I seem to recall that the BUF boycotted this election. If we utilise some applied handwavium and have Mosley win, there are a few things to consider in foreign politics: Italy, France and Britain are at this point semi-united in the Stresa front, and Italy's rather dodgy invasion of Ethiopia is going sufficiently badly that they're prepared to sit down with France and Britain to sort out a compromise. Given the French political situation, you might see another rightist party or coalition gain power there, and the three countries forming a pro-status quo in Western Europe alliance.
There tends to be a distinct difference in conduct between political movements in opposition and in power, and I don't see any reason that the BUF would be any different - Mosley isn't a traitor, and Britain hasn't been overrun by panzers, so I don't see any real reason for an alliance with Germany to be on the cards.
There tends to be a distinct difference in conduct between political movements in opposition and in power, and I don't see any reason that the BUF would be any different - Mosley isn't a traitor, and Britain hasn't been overrun by panzers, so I don't see any real reason for an alliance with Germany to be on the cards.