Historically speaking, nothing would really change, except britain would probably lose as Mosley was convinced Germany was too scary and powerful, so couldn't be defeated so would be more likely to surrender at the first sign of trouble. You'd just have two frances.
Maybe if they came to power early enough it could mean britain having a larger airforce, as they believe air was the future of war and the lack of a large airforce was why britain would lose the war.
But like, the amount of compromises they'd need to stay in power and enlarge the air force would mean that's all they'd be able to change.
And we're talking about people who weren't even able to hold their party together, so there'd be alot of compromises, it'd probably just be a Labour government with BUF cabinet ministers giving alot of speeches but not really doing anything. And lots of infighting and scandals to sap away national unity and resolve.
But really, they'd still be on the same side of the war, the policies wouldn't really change, things like the Land Army management, were taken from the british fascists. Really the conservatives in WW2 did more radical reforms than the BUF were proposing to do.
The B.U.F. didn't really want to change very much in the short term, basically it'd be if a completely rubbish and incompetent version of the labour party came to power.
If it's not the historical B.U.F. if you put the British Nazis in power somehow, you could get something interesting.
Maybe India would be independent as the BUF talked about that alot, but more likely, it was empty talk and nothing would happen if they came into power, especially with a war on the horizon threatening that india would be needed. The same with their ideas for developing the colonies to be able to absorb british goods, no way would they do that if they needed to keep exploiting the colonies to fight a war. Or the Empire would be more self reliant, as not importing grain from europe was a big policy, but really, during WW2 britain did all that anyway. so no change just alittle earlier.
So basically, nothing would change except it would be Mosley being used to sell dogfood today instead of Churchill, or Britain would have lost the war, Mosley would have died in prison and someone like Fuller or Joyce (Lord Haw-Haw) heading an unpopular puppet government, someone middle of the road conservative leading a by circumstance puppet government, that probably wouldn't be as unpopular as it wouldn't be seen as as willing but, would be hated.
Germans were really hated at the time, not because of Nazism but because of WW1 and the years of anti-german sensationalism before it so no one working with them would be ok.
But really, It's just two frances.
If you say the Fascists came to power before the start of the game, you could do something fun like, the war starts over Austria with the UK and Italy going to war against germany? as some fascists wanted that back then. Or just make them more pro-nazi or go with the british nazis, but them being a government is even more out there than the BUF who like, could atleast be said to have reconciled with Labour or something and come to power by wearing blueshirts instead of black and not being seeing to be too foreign? But if they went more foreign, more fascisti or nazi, then they become more impossible
This was a real possibility back at the time. Churchill was very much the main factor against it happening.
He really wasn't. Mosley repeatedly doing the thing least popular, fanboying over mussolini and having no control over his own party or it's public image was a main factor against that happening.