"I thought we had global warming now....600,000 years ago the weather was warm enough to support hippos in England and the sea level was so high that england was connected to the rest of Europe..."
It was the fault of caveman Georgio Buzhius the Old (called "Ugg Dub" by his friends) of ancient Mesopotamia, who caused the earliest global warming.
Wouldn't that be a low sea level? Which is associated with glaciation.
Sea level changes and Glaciation are why England has snakes and Ireland doesn't.