That was a good question. Evidently you will need a new front derailleur, specifically this:http://www.shimano.com/publish/conte...-.fd_road.html. Turns out that the cable pull from the flat bar shifters is different than the road shifters, so the Tiagara you've got won't work. Also, I don't see a V-brake equipped Novara Randonee on the web. They all have cantilever brakes which will work with the levers I linked to previously. Did you change the brakes after purchase?

Edit: Lots of good advice here, but some conflicting, and probably confusing. Here's the breakdown:
-Flat bar shifters have different cable pull than road brifters on the front shifter (this assumes indexed front shifters), so you will need a new front derailleur. A mountain bike front derailleur would work but it's cages are not curved to follow larger road chainrings, so I'm not sure how well it would work. The FD-R443 has "mountain" pull, but "road" cages, so is ideal with a flat bar shifter/road crank setup.
-You can use mountain bike shifters, but they don't have an extra click for trimming the front derailleur, which is more important with the larger road chainrings. (exception: Sram micro front grip shifters)
-As Fietsbob said, you could run a single rear, indexed, mountain bike shifter combined with a friction thumb shifter and keep your existing derailleurs. Very functional and economical, but a bit frankenbike'ish.
-You could also run grip shifters with a micro front shifter (which is basically friction). This would allow you to use your existing front derailleur. The downside is that the numbers on the front shifter indicating what gear you are in would not match up. A non issue for me as brifters don't have gear indicators either.