Not sure if i can be of much help on this one, i must be honest and say that i am not up to speed on this subject, but i have been digging around my collection of Galloway books. It seems that the axe heads found in Galloway can be traced back to the main sites at Craig Lwyd (Wales), Tievebulliagh & Rathlin Island (N Ireland) and of course Langdale (Cumbria). Axe heads are found mainly in the areas of Luce Bay & Wigtown Bay and to a lesser extent around Loch Ryan.
Around the coastal area of Luce Bay alot of flint tools can still be found, it seems the coastal areas provided a large supply of flint pebbles which were worked to supply alot of the tools they needed.

Brian