Both have already been mentioned but I'll echo Perry Miniatures and the Saga characters. I don't like the GB line models but their more recent standard bearers and personalities have raised the bar. Footsore Miniatures make some beautiful figures. The majority of these are Dark Age rather than medieval but the Normans may be near enough to your preferred era. Too old or no the Arthurian models and petty Kings are characterful figures that are a joy to paint.