The UK and ECHR
That is total ignorance. The ECHR was set up post World War 2 by the Council of Europe, way before the EU was thought of. It is not and never has been an EU initiative, although it has been incorporated into EU law, as it has within the UK.
This means that everybody in the UK is covered by the laws, regardless of origin, nationality, sex, ability, colour or any other difference or similarity to you and I. Nobody is exempted by anything.
Everybody, therefore, has the right to a fair trial, whatever the cost involved.
https://fullfact.org/online/european-court-of-human-rights-not-eu-court/
https://www.libertyhumanrights.org.uk/issue/what-is-the-echr-and-why-does-it-matter/