Mark boundaries are almost pretty much the same for Edexcel multiple choice, [Out of 24 - the actual paper mark. But marks are given out of 40] (21 +/-1) A*, (18 +/-1) A, (16 +/-1) B, (14 +/-1) C. Don't think we need to go lower. It depends on how 'hard' the test is. You will have done fine. I was always surprised with C1, B1 and P1 marks.
And Maths, On the results sheet it is 108/120 A*, 96/120 A. I don't know the others, and I also don't know the actual paper marks. They're probably halved as they're out of 60, but don't count me on it. I think it might depend on the percentage of marks you gained.