Issues with disabled radio buttons in dark mode

[GCHQ-Developer-847]

Summary of the bug

Disabled radio buttons in dark mode turn white when you hover over them. Disabled selected radio buttons display with a white outline which doesn't match the designs, and they turn blue when hovered on.

🪜 How to reproduce

Tell us the steps to reproduce the problem:

1. Go to the Disabled radio button story in dark mode.
2. Hover on the buttons.
3. See that they change when hovered on, and the selected variant displays a white outline when it should be black.

📸 Screenshots or code

🧐 Expected behaviour

The radio buttons should not change on hover at all and the selected disabled variant should have a black inner outline to match Figma.