Thanks for bring your obvious expertise to this query, really appreciated. Also for confirming why it took me so long to try and get my head around, then only roughly of course; as you say it's quite a mixture of rock types in this area.
That map's great, I did find some others but nothing that clear, a great find ! It's key shows just what a difficult subject geology must be to study, at least if your memory is as porous as mine, so thanks again, J.