I just checked Mercury (US based, not UK I know), and they support business accounts for founders living almost anywhere including most of Africa, but sadly not in the Democratic Republic of the Congo
"Prohibited Countries
We currently can't open accounts for founders living in the following countries: Belarus, Burundi, Central African Republic, Congo, Democratic Republic of the Congo, Cuba, Iran, Iraq, North Korea, Lebanon, Liberia, Libya, Nicaragua, Pakistan, Russia, Somalia, South Sudan, Sudan, Syria, Venezuela, Yemen, and Zimbabwe."
If you lived in some of the neighbouring countries of the DRC like: Rwanda, Tanzania, Zambia, Uganda, Angola it would have been fine. I wonder if it works with a DRC passport but you can show you live in one of the listed countries. It says "living in", not "citizen of". And a DRC citizen living legally in the US or the UK would have no problem opening a bank account.