I'm looking for any remnants that might be known of these cultures: personal names, place-name elements and beliefs. My eighteenth-century characters are going to meet with people who can't handle iron, therefore (for story purposes) must be from the Bronze Age or earlier.
Wikipedia and its likes are unhelpful. I haven't found a language site that goes into pre-Celtic elements, either. Likewise my trusty 'New Larousse Encyclopaedia of Mythology' and Stephen Oppenheimer's 'Origins of the British.' There are plenty of books on Celtic folklore and mythology in my local library, but that's too modern for my purposes. I've got access to jstor but some pointers as to where to begin with that would be most helpful.
I'd be most grateful for any input!