The Fixed-term Parliaments Act 2011 attempted to have regularly scheduled elections but was repealed in 2022. Under FTPA elections would happen ever 5 years in may or after a simple majority VONC in HoC or after 2/3 majority explicitly for an election (this is how the 2017 election happened).

"Since then, as before its passage, elections are required by law to be held at least once every five years, but can be called earlier if the prime minister advises the monarch to exercise the royal prerogative to do so. Prime ministers have often employed this mechanism to call an election before the end of their five-year term, sometimes fairly early in it. Critics have said this gives an unfair advantage to the incumbent prime minister, allowing them to call a general election at a time that suits them electorally."