Oswald Mosley was a popular British fascist who tried to turn the UK into a fascist country. Oswald Mosley held fascist rallies with incredibly large turnouts. Over 80,000 people turned up to hear him speak at Earl's Court.
Oswald Mosley was imprisoned and his political party was disbanded. Was there any public outcry, and how did the government deal with it?
I think you are misrepresenting Mosley's popularity in your question there. Earl's Court was a peace demonstration including large groups of left wing and pacifist support as well as sympathetic right wing parties. It wasn't just to hear him speak. He had manoeuvred on from portraying himself as a facist and was rebranding as simply a "peace negotiator" showing his constant populist fluidity.
He was unsuccessful in elections on his facist ticket and even optimistic estimates only put his membership at its height at around 40-50k nationwide. By the time of his arrest he had already "peaked" a few years earlier in 1937 especially after the PR disaster of cable street (A much more usual march of about 2-3k)
There was no public outcry, the UK was at war with facism at the time and he had already lost any semblance of support he had years before. He had support from certain upper class families (mitfords for example) which probably contributes to his early release.
Oswald Mosley and the New Party - Matthew Worley