Fixed guidance based on review feedback

src/components/radios/index.md.njk

@@ -27,7 +27,7 @@ If you are asking just [one question per page](../../patterns/question-pages/#st
 
 Read more about [why and how to set legends as headings](../../get-started/labels-legends-headings).
 
-Users can only select one option from a list of radios. Do not assume that users will know how many options they can select based on the visual difference between radios and checkboxes alone. 
+Unlike with radios, users can only select one option from a list of radios. Do not assume that users will know how many options they can select based on the visual difference between radios and checkboxes alone. 
 
 If needed, add a hint explaining this, for example, 'Select one option'.
 
@@ -36,7 +36,7 @@ Do not pre-select radio options as this makes it more likely that users will:
 - not realise they've missed a question
 - submit the wrong answer
 
-Unlike with checkboxes, users cannot return to an unselected group of radios once they have selected one, without refreshing their browser window. Therefore, you should include 'None of the above' if it's a valid option. 
+Users cannot go back to having no option selected once they have selected one, without refreshing their browser window. Therefore, you should include 'None of the above' or 'I do not know' if they are valid options. 
 
 Order radio options alphabetically by default.