Are you going after the Norse and other figures too (in addition to Empire)?
Keep in mind that Foundry produced some of these as historicals (Norse = Vikings, Bretonnians = Feudals, Nippon = Samurai, etc.) long after GW ceased production. In fact, I got some of the Samurai from Foundry at one point, and I believe they still had the GW/Citadel markings on the bottom. None of the Foundry models I had from any of those series had slotta bases, though.