Ice age Britain
During ice ages Northern Hemisphere glaciers advanced southward over the British Islands (and Doggerland --see below) and drove back humans (Antecessor, Neanderthal, Sapiens Sapiens who had settled and hunted thereon. When the Ice sheets most recently retreated due to cyclical warming, the remaining hominims (homo sapiens sapiens) returned and eventually adopted the Celtic ("Gaulish") culture showing most similarities to the Celts of northwestern Iberia. The earliest indication of people currently known in the British Islands are footprints of (assumed) Homo Antecessors in Happisburg in southeastt England, now dated to ca. 600,000 BC.

Glaciation in Britain -- https://www.geolsoc.org.uk/ks3/gsl/education/resources/rockcycle /page3585.html
People of the ice age in Britain -- https://iceageworcestershire.com/people/
Next world Ice age -- https://www.dw.com/en/earth-next-ice-age-prediction-when-v2/a-71786018
Last Glaacial Period (wiki) -- https://en.wikipedia.org/wiki/Last_Glacial_Period
Happisburgh footprints -- https://en.wikipedia.org/wiki/Happisburgh_footprints

https://en.wikipedia.org/wiki/File:UK_Happisburgh_c._800000_BP_EN.svg
Map showing the location of Happisburgh during the early Pleistecene, about 800,00 years BP.
During the glaciations, Atlantic water level dropped about 130 meters extending shorelines and exposing the Doggerland land bridge between the islands and mainland europe.

https://en.wikipedia.org/wiki/File:Happisburgh_Footprints_01.jpg
About 50 footprints were found in the study area (about 40 square meters) representing about five adults and children thought to be Homo Antecessor who also have been identified in in the Atapuerca Mountains of Spain about 800,000 years ago. No hominin fossils have been found in Happisburgh. (Homo antecessor lived before the ancestors of Neanderthals split from the ancestors of Homo sapiens 600,000 years ago.)
HomoAntecessor

Happisburgh handaxe ca.600,000 - 800,000 BP.
Beween 2005 and 2010 eighty paleolithic (old stone age) flint tools, mostly cores, flakes and flake tools were excavated from foreshore sediment dating back to 950,000 BP and thought to have been made by Homo Antecessor.

Homo antecessor -- https://en.wikipedia.org/wiki/Homo_antecessor
Homo Antecessor is thought to be an ancestor of both Homo Heidelbergensis and Homo Neanderthalis Sapiens and also may be an ancestor of Homo Sapiens Sapiens.

Homo Heidelbergensis -- https://www.mpg.de/18837550/0621-evan-britains-earliest-humans-150495-x

Homo heidelbergensis, an ancestor of Neanderthals, occupied parts of Britain between 560,000 and 620,000 years ago, specifically in the southern region when it was still connected to Europe. Discoveries in Kent, England, including stone tools and evidence of animal hide processing, confirm their presence during this period. The site near Canterbury is considered one of the earliest Palaeolithic sites in northern Europe.

Homo Heidelbergensis is considered to be an neanderthal ancestor.

Doggerland: Ice Age Atlantis(?)
Named after Dogger Bank cod fishing (mostly) area in the North Sea, which was itself named afte a kind of Dutch medieval fishing boat called a dogge. What is now called Doggerland is the large area (yellow in the image) submerged by sea level rise due to melting ice as the last glacial period has been ending (ca. 10,000 BP).

Doggerland was inhabitted by pre-humans and then Homo Neanderthalis Sapiens and then by Homo Sapiens Sapiens, and was rediscoverd when artifacts were brought to the surface in fishing drag nets. Over the course of several glacial and interglacial phases hominim hunter-gatherers were able to follow game animals across Doggerland to what became the Brittish Islands. During glacial phases, the hominims were either forced by ice sheets and cold to retreat back to mainland Europe (or die out). there were periods covering many thousands of years during which no evidence of habitation of the Brittish Islands have been found. During interglacial periods Doggerland may have been partially of completely submerged, only to re-emerge then the next glacial period lowered sea level again. It is estimated that during glacial periods the sea level of the Atlantic could have been as much as 130 meters (about 500 feet) below what it is today. Note that we are still recovering from the last glacial period: most of current global warming and sea level rising is part of that recovery and is not human caused.

Doggerland artifacts are the remnants of the prehistoric landmass that once connected Britain to mainland Europe, now submerged beneath the North Sea. These artifacts, discovered through beachcombing, dredging by fishermen, and archaeological surveys, include a variety of tools, bones, and other remains that shed light on the lives of Mesolithic hunter-gatherers who inhabited the area.

Types of Artifacts:

Stone tools:

Arrowheads, axes, hammers, and adzes crafted from flint.
Bone and antler tools:

Barbed points, spearheads, and other implements used for hunting and fishing.

Human remains:

Fragments of skulls, jaws, and teeth, along with evidence of butchered bones, suggesting burial practices and dietary habits.

Animal remains:

Bones of mammoths, lions, rhinoceroses, and other animals that roamed Doggerland, providing insights into the ecosystem and fauna.

Other objects:

Birch tar grips, peat samples, and even footprints preserved in the sediment.

These large and small barbed spear points and arrowheads were carved from bone and antler by Doggerland’s Mesolithic inhabitants.

The jawbone and teeth of a Mesolithic hunter-gatherer that lived in Doggerland around 8,300 years ago were extremely well preserved by the oxygen-free peat environment under the North Sea.

A 13,000-year-old aurochs or bison bone etched with a zigzag design was recovered near Brown Bank.

Fragment of a hammerstone was discovered at the Southern River estuary site.

Doggerland "Wood Henge" revealed during an exceptioally low tide

Maditerranean mep error -- Note that during this period of glaciation the Atlantic sea level would have lowerered to the point that there could be no Atlantic inflow over a Gibraltar land bridge. The Mediterranean would have been mostly dried out because river inflow could not keep up with surface evaporation.

Ice Age Mediterranean (?) -- As with Doggerland, much of the Mediterranean was exposed dry land during glacial periods, and much of that dry land was inhabited by sequential hominim hunter gatherers. At some point after the melting got underway there was a great flood that modern investigators think could have quickly refilled the basin. Shortly thereafter, maybe concurrently, the Black Sea would have refilled -- Biblical Flood? Also, note that the Nile River delta, which almost certainly would have been inhabited (Shown, lower right corner of the image) is thought to be as much as 1500 feet below the current delta.

Brittain -- Geology/Geomorphology
Brittainis and always has been a geological jumble with lots of uplifts and overlays.

The oldest exposed rocks in Britain are found in NW Scotland and the western isles (Hebrides +). This ancient Lewisian gneiss is almost 3 billion years old. The oldest in the world are in Canada. The Scottish Highlands are mainly formed from metamorphic rocks formed around 400-450 million years ago. Ben A'an shows foliated mica-schists exposed at the top.