The North Sea has yielded up some Neandersecrets, thanks to some intrepid Dutch scientists. There is an article here, and here's a picture of what they found, which, though not much, should give us all an idea.
Of course, there seem to have been other finds in the area, though no fossils until now. But there is evidence that Neandertals existed in what is now the UK, some 60,000 years ago; some fairly typical "Neandertools" were found near the remains of some hapless woolly mammoth, in Norfolk, a few years back. And there wasn't any North Sea between Britain and the Netherlands 60,000 years ago, either. They could just follow the reindeer/caribou, or the woolly mammoths, or whatever they were inclined to eat at the time. . . .
Which is all very nice for my heroine Illg, who, with her companions, recognizes places where her "Ancestors" have been.