I think "и на том спасибо" does not fit here at all. It's a "false" gratitude for something that it less than adequate, while Dursleys are sincerely proud of their way of life and are sure that this is the only way.
"Большое спасибо им за это" is not good either. Do you thank Dursleys for being normal?
Не нужно это дословно переводить, ерунда получается.

I do not agree with "Бирючный проезд". Бирюк that's ascetic, he leads a lonely life, boring. There's not a wilderness.
It's from "бирючина" ("privet", a plant), but I agree that 99% don't know of this plant. I also wondered why they translated "Privet" as "бирюк" until I checked 'privet' in the dictionary.

Бирючина колючая, может перевести это как "Колючий проезд" или каким-нибудь другим производным от слова "колючки"?