This is a question I had when I took M8 earlier in the year and found the answe in the syllabus document in the Study & Qualifications section of the ICB website for the Level 3 qualification. Snip of the wording below. Hope that helps.
"Once all assessments have been successfully completed an overall qualification certificate is awarded. The qualification certificate will be graded at Distinction with Honours, Distinction, Merit or Pass. Unit percentage results will be averaged.
The following average % marks show an example of how the final grade might be awarded (note the same range of marks may give a different overall result depending on the number of Passes, Merits and Distinctions achieved): Distinction with Honours 98% and above (all five assessments being graded at Distinction) Distinction 95-97% overall (all five assessments graded at least at Merit or Distinction) Merit 90 – 94% (a mixture of individual grades) Pass 80 – 89% (a mixture of individual grades)"