Carvings on Jersey have been provisionally dated to 14000 years ago, in the warm period between the Oldest and the Younger Dryas events. It appears that Palaeolithic art of the Magdalenian culture who thrived between 16,000 and 13,000 years ago in France and Germany, got as far as Britain (still connected to the continent at the time) – see www.bbc.co.uk/news/science-environment-34679202
See also http://phys.org/print365756628.html … the excavation is ongoing and this is a press release.