I guess #1 is more of a complete sentence. By saying “The”, you’re simply implying that you are referring to.... “people”. Orrrr for example, if you are writing an essay, when talking about the topic in the first paragraph you would probably start the sentence with “The....”. BUT, if you already wrote the topic of your whole essay, you can start the sentence with “People in the UK....”. It is ok not to use “The” every single time.
Soooo #2 isn’t wrong either. They’re both literally the same.