Certain areas of the Atlantic area - like Britain - spoke an East European language? Seriously?
No offense, but that claim is just outlandish. You might as well claim that the Atlantic seaboard spoke Algonquian, Salish or maybe Tibeto-Burman, such a claim would be just as plausible, and just as well grounded on the available evidence.
I might add, I'm not ruling out that the Venedi of European Sarmatia (in particular the "Venedic" peoples further interior that would qualify as candidates for the actual Proto-Slavs) were actually speakers of Balto-Slavic (rather, I made that possibility because in the 2nd century, Proto-Slavic and the Baltic languages would have been still very close, this is very clear from internal reconstruction). But, my objection is that 1) the medieval usage of "Wends" is clearly as an exonym, therefor we don't know that for certain, and 2) the Venedi lived much further east (former East Prussia - modern the Kaliningrad Oblast, Lithuania, perhaps Belarus), while the area of the "Wendish" (West Slavic) peoples was firmly Germanic in the 2nd century (read below).
Its not my opinion, but I sense that you're not going to accept the following paragraph because you've declared earlier in this thread that according to you, linguistic is supposedly a "weak" science. In any case, Greek and Roman geographers describe the ethnic groups of Germania in sufficient detail.
As I said, the tribes of the general area of modern eastern Germany and western Poland (between the Elbe and Oder rivers, but you could extend that to the Vistula) have clearly Germanic names, including the
Langobards,
Suebi and
Burgundian, or would you say that the bearers of the contemporary (2nd century AD) cultures of these areas - the Jastorf and Przework cultures - spoke something else than Germanic?