Who is the wali for nikaah in the absence of the father?

I am a Muslim Arab born and live in the U.K. I'm in the process of marrying an amazing Bengali girl. There's just one problem, her father and mother were divorced ages ago and she hasn't seen her father in 4 years. She has tried to contact him to be her wali as that's what the Quran says but no reply. It's been about a week and half but we want the nikah to be as quick as possible so we don't delay it. What should we do? Should we wait till her father replys no matter how long we wait? Her father has no family here in the U.K. either?