Hiya
Pretty hard to find exactly what you are describing so i see your problem! Even with all the information you have given its hard to guess your personal style and what you won't like though. had a lil peek at your profile picture and i must say you are stunning (and your children are adorable), i thought that charcoal, bluey greys and classy neutral tones would look lovely so i had a look along those lines. Fortunatly i am both a fashion design student and an insomniac with sleepless time on my hands . Hope some of this might be of use to you;
I do actually have two dresses myself which sound similar to what your after but one is a miss sixty wool dress, and the other a H&M mohair/acrylic mix dress both about 3 or 4 years old, seems to be hard to find ones like these with buttons this season. But had a go.
on Asos.com -
firetrap cable knit wool cardigan, 50% wool about 80quid or fullcircle chunky knit wool blend cardigan you could wear both with leggings as a dress, they are both fairly long and very snug looking with really nice knit details.
*princess tam tam cashmere dress in grey brown and violet, simple but chic with a few buttons and looks really snuggly 70quid
Marksandspencers.com -
Per una front frill knitted dress in charcoal (no buttons but low front), i know its not what you want but i think it would look gorgeous. Slims over the hips, and has a ribbed panel in the middle with a delicate knitted frill down the front perfect to detract from stomach area- its 59.
I'm afraid I don't know that much about clothes which are good for breastfeeding, but i found a website that might give you some more options, babeswithbabies.com theres a lovely cowl neck sweater-type dress on there, and loads of great underwear -which i always think is most important to feel fabulous !
Check out allsaints website as well they have some lovely cotton and wool fine knit dresses, really fashionable and elegant. kade dress is nice.
Hope you find what your looking for, and maybe i was a little bit of help, I'll keep an eye out for anything else. Going to try and get a wink of sleep now as it is nearly 7am and almost light again... yawn.