Omitting Sixth Form/A-level grade from resume

I schooled in Africa and won an award as  the overall best student in my Sixth Form class. However, because the grading system is presumably unfamiliar to people (recruiters & bankers) in the UK, I usually only mention my award as the overall best in my class and omit the A-level-equivalent grades from my CV, would that hurt my chances of getting an interview? (I am a master's-level student and my undergraduate grades are first-class equivalent).