hey hun! I went through the same size break down before my ba lol
I was 34a, 5ft2, 8 stone, size 8 and I went for 380 CUI partial unders in the end as i wanted to be a D cup.
I am so glad i went for them in the end. I now measure 32F but look around C/D. I defo dont look top heavy, they suit my frame perfectly.
Sorry i cannot give you any advice about the responsives but im sure you will be happy with the 325’s. They will be gorgeous for your figure x x x