of number four, Privet Drive => проживающиe в доме номер четыре по Бирючинскому проезду
Дурсли or Дёрзли => I'm inclined to say Дурсли since they serve an exaggerated example of the so-called "normal" or "simple" in a sense of stupid and narrow people, and hence Russian "дур" serves pretty well here.