Right, and take the salt you can get at places like Maunguid, Pengwern and Licidfelth and take that back into Wales. Ideal trade route. Only difficulty is keeping away from bandits and finding places to sell the excess stuff (because you'll always have more goods than you can sell at any one town).
Especially good idea: Hit the villages around towns line Pengwern and Licideflth to grab a lot of really cheap salt (talking about 40-100 scillingas) and then take that into Wales, sell it around for 250-300, buy minerals there for 40-100 scillingas, and sell it around northern Brittania for 380-500 scillingas. You can make a lot of money very quickly if you do it smartly, and the risk from bandits is actually pretty low in that route.
Also if you really want to accumulate renown? Be a Bard. It's also good for a few extra scillingas to help you cover the expenses of travel. And the sweet part is, you never LOSE renown while barding, even if you lose bardic reputation, so it's probably the single most dependable way to raise renown.