My new favourite work dress came from H&M in the sale, I love H&M for maternity wear, but they seem to have a bit of an odd mix in there at the moment. I've also just had a look through the next sale, and they have a lot of mat stuff in there. Might be worth a try?
I wore an enormous amount of isabella Oliver and seraphine stuff for work and casual. Lots of the IO tops work for breastfeeding too and are stretchy enough and ruched not to look baggy after the bump goes (having accommodated what was a BIG bump in my case!)