It's pretty much impossible via the Baltic (too many larger peoples in the way) and the Livs, Kurs and Lithuanians are pretty much hemmed in in any case. The Finns and Ests on the other hand have real possibilities.
Someone did a TL about a Finn independent Kingdom showing the Finns starting out with 50,000 people. Eric Flint, in one of his historical novels, points out that in the early Middle Ages, Finns lived in what is now Swedish Nordland, living as hunters and gatherers where it was too cold to farm, while the Norse occupied the Norwegian Sea Coast all the way up to Lapland. Of course the Swedes finally conquered the entire Scandinavian Peninsula east of the Kjolen Divide, driving the Finns east of the Gulf of Bothnia and eventually, after the Little Ice Age caused famines decimated their numbers, conquered the Finns too. But what if, under pressure from the Swedes and the Novgorodian Russ, the Finns take the Norrland coast of the Norwegian Sea, start by going "a viking" and then collectively decide to migrate to and conquer all or part of England?
50,000 people means about 20,000 combatants, which is a respectable sized army for the time. And there's enough wood to build enough ships to carry them if they decide they can pull it off. Finnish ihfluence on English would be interesting indeed. We would have an English language that sounds a lot like Tolkien's Quenya or Elder Tongue (since that language was based on Finnish), for one thing.
Mae govannen!