Sounds cool!

What do the commoners think about their lords, though? I mean, the vampires feed from this lot, right? Are they all living in terror, or is there like... I dunno... a sub-class of commoners who are offered up to the Nobles as food? Or is it like, "Ooh, it's such an honour to be food for the baron!" I mean, I guess it'd depend on what kinda experience it is to be, uhh... bitten.
It kind of depends on the province I guess. Here are a few examples:
Province A is ruled by a very sadistic Lord, so naturally, the commoners live in constant fear. Commoners are chosen at random to be sacrificed as food at regular intervals. The Nobles may harvest more or less people depending on simply their mood or if their constituents have been "misbehaving" lol. Those selected to be food are basically facing a death sentence since the Nobles here prefer to drain their victims dry (it's not good to waste food, after all lol). Therefore, the Nobles in this province basically see the commoners as nothing more than cattle.
Province B is ruled by a more benevolent Lord who calls for volunteers. The volunteers, in this case, are not killed, but simply fed upon to a certain extent. The logic behind this approach is that the blood of willing individuals tastes better than those who are in a state of fear/anxiety. This is because the Human body will release different hormones depending on their mental state. Generally speaking, a positive disposition correlates with better tasting blood. On one extreme would be a Human that's in love or infatuated vs the other end of the spectrum where a Human is in a state of peril, facing inevitable doom. So in this province, the commoners may actually consider it an honor to be selected. These volunteers may even be given preferential treatment, such as better food, shelter, and etc. So it's kind of like upper-middle-class vs lower-middle-class of the other commoners.
Province C might be ruled by a more "efficient" Lord. In this case, all the commoners are called together to offer a small portion of their blood. Perhaps they are gathered in the town square every now and then and told to spill some of their blood into a single shared container/cauldron/barrel. This is basically akin to "taxing" the people.
Province D could be ruled by a Lord who's House enjoys "the hunt". Therefore, no warning is given as to when they decide to harvest. Instead, the commoners live in perpetual fear as they are hunted down during the night at random.