The major differences in the British Isles are mainly to the various 'waves' of the same people arriving there from the same Franco-Iberian Ice Age refuge. There are very subtle differences detectable in the DNA of each wave...I believe he said 18 waves. It is only when the DNA from the other Ice Age refuges (R1a's and I's - Ukraine & Baltic ) begin arriving along the eastern areas that another DNA influence is detected. He says that 85% of the British DNA today is ancient and arrived very early.
90% of the Irish are R1b's as are 70% of all other Europeans.
Bryan Sykes says that the Thames and the Rhine were once the same river.
THE NORTH SEA. From Earth in Upheaval.
The stormy North Sea, brodered by Scotland, England, the Low Countries, Germany, Denmark, and Norway, is a very recent basin. The geologists assume that the area was once before occupied by a sea, but that early in the Ice Age the detritus carried from Scotland and Scandinavia filled it, so that there was no sea left: it was all turned into land. The river Rhine flowed through this land and the Thames was its tributary; the mouth of the river was somewhere near Aberdeen.
In post-glacial times, so it assumed, in the Subboreal period, which began about 2000 years before the present era and endured until 800 BC., large parts of the area were added to the sea. The Atlantic Ocean sent its waters along the Scottish and Norwegian shores, and also through the Channel that had been formed only a short while before. Human artifacts and bones of land animals were dredged from the bottom of the North Sea; and along the shores of Scotland and England, as well as on the Dogger Bank in the middle of the sea, stumps of trees with their roots still in the ground were found.
Forty-five miles from the coast, from a depth of thirty-six metres, Norfolk fishermen drew up a spearhead carved from the antler of a deer, embedded in a block of peat. This artifact dates from the Mesolithic or early Neolithic Age and serves as one of many proofs that the area covered by the North Sea was a place of human habitation not many thousands of years ago...