Is there a map of when Great Britain was connected to mainland Europe?

Yes, there are several maps that depict when Great Britain was connected to mainland Europe. This period of geological history is known as the Doggerland, which was a land bridge that connected Great Britain to the European continent during the last glacial period. Here is a map that shows the extent of Doggerland:

[Image of a map depicting the Doggerland]

As you can see in the map, Doggerland was a large area of land that stretched across the southern North Sea, connecting Great Britain to mainland Europe. It is believed that the Doggerland was flooded around 8,200 years ago due to rising sea levels.