That's still a bit of a mystery, as we only have two ships from this period, all of which were selected for ritual destruction in a single swamp near the current Danish-German border. These ships do look like they married Roman/Mediterranean shipbuilding innovations with Scandinavian iron age traditions, but they did not have the robustness and seaworthyness of ships of the 8th century. They also lacked a sail, which makes crossing the North Sea harder (but not impossible). However, whether these two ships, which were clearly warships intended for raiding in the Baltic sea, are representative of Scandinavian ship-building ability is still a huge open question.

More likely is that any Scandinavian-British shipping would have followed the European coast until crossing over somewhere near the Flemish coast, as ships had done from the Bronze Age to the Roman period. Even deep into the Medieval period, this route was preferred. Whether it was theoretically possible to make a direct crossing is unprovable, however. The lack of direct contact between Norway and Scotland until the Viking period, however, suggests that even if a daring Germanic adventurer would have been able to survive such a crossing, it would not be a regular occurrence.