It's one of those anomalies, we believe that there were at least hunting parties visiting (we were still joined by the land bridge to mainland Europe) despite the ice cover, it was probably riven with water flows anyway. Farming settlements seem to come late to these islands though.
Parts of Scotland are still rising from the removal of the weight of the glaciers, even today.
The dates you give are right for the Neolithic farming revolution, but at it's roots in the Fertile Crescent..........I'm told that similar dates hold true for S. America, China, Korea, India and Africa...........Australia doesn't seem to for some reason
Maybe they didn't need the extra resources farming provided ?
There are archaeologist today who still kind of consider the Roman's attempted conquest
as the Iron Age here
We talk of the Pictish Kingdoms as the structured societies that grew as a response to the pressure of the Romans and then the Angles upon the Iron Age tribes of Alba/ Caledon. They were stronger as 'nation' than as 'tribe' or 'clan'.
cheers,
Toddy