You can google "X white minority", I recall reading some papers on it when I was going down an immigrant assimilation research rabbit hole (I'm an immigrant so it's a topic that fascinates me).
https://bamproject.eu lists some cities along with data (e.g: Malmo, Amsterdam, etc).
Citation, if you are able?
For sure London has a majority of people who are not 'White English', but I'd be very surprised to learn that 'White Everyone' is a minority here.