Hi there, if you have been recommened 340cc then go for it!! always opt for the bigger size your offered!. My friend is tiny and was a 32a and had 340cc and now a 32d!!. I also had 340cc but i was a flattish 34b after having 2 kids, and i had uplift and i measure a 32e, so i reckon you,ll def end up a d possibly a dd with a 340cc! and a 300cc i reckon you,ll end up a large c cup. Ill email you my pics!! i was only a 34b to start with so not that smaller than what you are now XX