I'm not actually at all tall (5'6") but I have a very long abdomen. I've bought some fab long vests from H&M plus a nice linen shirt, but I'd like a couple of fitted (not baggy) long sleeve tops that will fit right under my bump and over my hips .
M&S have some long cotton tops in their Limited Edition range. I need long tops too, but more cos they ride up over my belly and boobs! I found a nice navy one in M&S that's scoop necked and comes down to my hips (also makes me look v pg, but hey).
I just bought one from our local maternity clothes shop - it's just what you describe, v-neck and black and it's by Veronique Delachaux (so I'm guessing it's French!). That probably doesn't help much, unless you can get to Bristol.
The H&M vests are working for me too - and I am hearing good things about Top Shop basic tops from my friends as well...
I am pretty tall (6ft)and found it really hard to find mat clothes to fit last time. I shop alot at Long tall Sally which is for tall women but they only do 2 pairs of trouser for mat clothes so that is all the bottoms I had (one pair of black trousers and one pair of jeans!) Their tops might be ok but not mat. I found that for tops best to look in normal shops for those tops that are cut under the bust and come low. I have found that alot of shops are doing longer tops (perhaps they are in fashion!?) Not sure what size you are but I found that shops for larger women have longer tops eg Evans. Not much help if you are a 10 though!
I too struggle with clothes as i'm a 6 footer ! Dotty P's maternity is good and for those with long legs wanting more choice than Long t.sally, Fleur Uno who advertise in preggie mags will make trousers to the length u want for bout 25 quid.I also bought normal D.p's jeans which get longer the bigger size u get.
I've bought some belly belts from m&s. Basically, they're like a boob tube that go over your bump to hide the panel on maternity trousers. It gives the illusion that your tops are long. It means you can wear virtually any top. I think I paid £5 for each but they have a few colours.
Highlander, I'm 5'7" with a long body too. This pregnancy I have mostly been wearing Hennes, Top Shop, and some amazing brand called Noppies. I don't know where they come from because I got the clothes second hand from another mner.