Marks & Spencer bra sizing?

I can't find a bra that fits properly. I'm currently wearing a US size 32A, but the band is HUGE. I fit a 28D (US size) in the Royce brand, but the cup didn't really suit the shape of my . I tried a 28 A/B/C (US size) from The Little Bra Company, but they were all too small. The smallest I can find in Panache and Freya brands are 28C and D, but they're both way too big. There's a huge difference between the Royce 28D and the Freya 28D. Royce fit like a 32A while the Freya cup was way too big (cantaloupe sized when I have plums). How do the M&S bras fit? Is a 28D a small or large cup?