Now I know there is a plethora of quests at the Tarant thieves' guild, I was only given the initial sewer map quest and statue of Kree quests before being told there were no more quests available.... Any ideas?
Yes, you simply go to different npc(s) for all the other thieves guild quests. There are a lot more than those two. Try the purveyors of stolen goods and any shifty sorts loitering on street corners.
The most recognizable and easiest to find thief would be the halfling woman at the Vermilion Station, what with not roaming the streets and having a unique appearance.
So I tried talking to the gnome lady in vermillion station, but no quest. conversely whats the quest she gives you? I'm pretty sure the only reason I got the Kree quest was because I already had the statue in my inventory.
The Kree quest is given when you're above a certain level IIRC. As to the the thieves' guild "quests" they don't show up in your quest log rather they show up in your notes. Steal the item, deliver it to the fence and then she'll give you more target items to steal and give to the fence; these items will still give you experience like a quest but strictly they don't register as "quests".
You get those quests by using the same lines you use to get rumours from bartenders, by the way. Saying this in case you dismissed those lines because of already knowing all Tarantian rumours and not expecting anything new from asking for them.