The Flipside of Dominick Hide (1980)

Dominick Hide, a time traveller from the year 2130, is studying the London transport system of 1980. Time travellers are supposed to be observers, and are strictly forbidden to land their flying saucers. One time traveller who broke this rule accidentally killed a dog, changing history and causing many future people to disappear. Inspired by his Great Aunt Mavis, Dominick decides to find his great great grandfather. He begins to land in 1980, where his strange clothes and speech make him seem an eccentric oddball. His quest brings him into contact with beautiful boutique owner Jane, and they fall in love. As Dominick's visits become more frequent and more prolonged, he increasingly risks his indiscretion being discovered by his boss, Caleb Line, and every moment he spends in the past increases the danger that he will catastrophically change the future

Unfortunately the movie The Flipside of Dominick Hide is not yet available on HBO Max.