Opening US Investment Fund from within the UK

I notice that some people here have investment funds in the US.

Did you all open them while you were still living in the US?

I have a retirement account with US Fidelity  that I opened when I was working in the US. They accept that I live in the UK, send statements to my UK address.

I tried to open a US brokerage account online, just to see if I could get through the application (since I already have an account with them), only to be told that they only take US residents. I get directed to the UK site.

I'm not particularly chained to Fidelity. Does anyone know of a US fund provider that will allow US citizens not resident in the US to open an account?

Have you had any luck? I've just posted a new thread after being told by my brokerage firm TD Ameritrade that they are closing all accounts for people living in the UK/ Thanks.

Haven't heard of anyone