What is or TV series where a girl vampire befriends human boy the intro sung with British accent something like Out in dark yada vampire?

You're describing the show "Being Human" (the British version).

Here's why:

* Girl Vampire: The show features a main character named Anna, who is a vampire.

* Human Boy: Anna befriends Mitchell, a human who is a werewolf.

* British Accent: The show is set in the UK, and the actors use British accents.

* Intro Song: The intro song features a female voice with a British accent, and it definitely has the vibe you're describing.

If you're interested in checking it out, "Being Human" is available on various streaming platforms.