Your own DNA alone can't be relied on, but if we suppose that a whole bunch of Greeleys have the same DNA because they descend from the same immigrant, then somewhere they probably have some very distinctive mutations that could help to pin down the immigrant, eventually. But those mutations haven't been identified yet.
When the companies talk vaguely about northern Denmark, southern Sweden and southern Norway, they mean that the identified mutations are relatively widespread, and so, relatively early. They might tell you something about where your immigrant's distant ancestors lived, way back in prehistory.
How that type made the journey to England is anybody's guess. A Y type can travel thousands of miles in one generation, e.g. in a Roman auxiliary. Or, it can make the same journey in hundreds of small steps, generation by generation, village to village.
The same Y type will have made other journeys in other directions. Many of those journeys will have ended in extinction without trace. Some may have ended in proliferation and an extant cluster. But that would have nothing to do with your own ancestry.
The woffle about land bridges is just the sort of padding that the companies make up to fudge over the fact that they don't have what they lead people to expect.
