I don’t care what the particular number is, but it’s a dart throwing game and you have to get all the numbers correct in one shot or start over

I think we can simplify this with one slider that covers the entire range of post codes: 00000 - 99999

Put all of the postcodes in a paginated list that displays only 30 entries at a time (60 and 100 per page for premium users), only has next/previous navigation buttons, orders the entries by popularity, and goes back to the first page if you reload the website. Or an infinitely scrolling page that loads each page dynamically, but returns 429 Too Many Requests if the user scrolls too fast.