I have both the Herbin CdB and the RK sepia and the RK seems to fit the bill for me these days. I thought the CdB looked like chocolate milk.
The problem with the topic of sepia ink is to actually determine what the color is you have in mind. Sepia as in the color of old fotos and actual cuttlefish ink (the real sepia ink) are two different things, and it's quite a varying range- from yellowish browns to mauve. You just have to find an example that, to you, typifies "sepia" then try to find a match with ink tints available. Having been there and done that myself, I can only wish you luck in your quest. If you're like me then you'll find the perfect match only to soon change your mind. It's quite vicious.
Do check out DCPritch's comparasons and recent threads showing actual squid ink based FP ink. And as always comparason tools such as Goulet's (isn't there one in Britain as well?) are your friend in these matters.
"What? What's that? WHAT?!!! SPEAK UP, I CAN'T HEAR YOU!!" - Ludwig van Beethoven.