[stan the beaver]

"Two separate groups may have been in competition"
Well, duh!

"The flake users may have come from a different part of Europe..." Think France.

[expat_panama]

400,000 years is an awfully long time.   Going back just 10,000 makes all of the (now called) British Isles just one continuous 'French' peninsula.   So going back 40 times as long could put this dig anywhere--- north pole? Caribian?.