If we take a look at the grade boundaries for 2022 (they will be slightly higher this year though) we can see:
A* - 217, A - 164, B - 130, C - 96, D- 62, E - 28
In %, 76%, - - 55%, -43%, - - 32%, - -21%, - - 10%
From edexcel: 9MA0 A Level Mathematics Subject 300 217 164 130 96 62 28 0
That means you are currently on a C (35 to 38% avg). If you did C-grade worthy in your mechanics then you'd get a C!
However, just because you could get a C doesn't mean you shouldn't think about what you could get - a B if you did really well!