Flin being a grain product, it should be Colovian - likely from the Chorrol area (since southern Colovia has its own wine production). I don't think the name Flin is out of place next to other native drinks such as Akul and Aliyew - it sounds Colovian enough. I've no objection to a renaming, though.
For the moment, I would put the brandy as a northeast Nibenese thing, or a product native to the Imperial City itself - explaining its exclusive and expensive nature. It would be made based on imported grapes from the West Weald.
Battlewine - I don't really see the point. We already have scores of different wines - in fact, I've proposed numerous times to replace the TR wines with PC ones, which have higher quality meshes and (imho) better, more realistic names. Also, some of our alcoholic drinks, like Akul, have a similar background:
Akul is a strong Colovian ale, brewn from malted barley and dried mandrake root. It is a bitter, earthy liquor with mild hallucinogenic properties, popular among soldiers and the Colovian nobility. It is supposed to bolster a warlike mindset, and help communion with war-gods like Reman or Shor.