Tabster,

You're off base there. Pretty much all archaeologists and ancient historians agree that Boudicca and her people were Celtic.

Your statement that there is no archaeological evidence is baffling. ALL the archaeological, historical, and linguistic evidence, down to the languages spoken in Wales, Cornwall, and Brittany, supports the contention that the pre-Saxon population of Britain was Celtic. Welsh and Cornish are both Celtic languages, as was the language of the Britons who lived throughout the island until the Saxon invasions. (And a good deal after, in some parts of the country such as Strathclyde.) The Bretons in France are descended from Britons who fled the island, and their language is Celtic to this day. There's no basis at all for saying that the Celts never settled "mainland Britain."

For the purely archaeological evidence, I'd recommend the books by Lloyd Laing, the most recent of which can be found here.

For linguistic evidence, see:

Jackson, K. (1953. Language and History in Early Britain.

Price, G. (2000). Languages of Britain and Ireland, Blackwell.

Sims-Williams, Patrick (2003) The Celtic Inscriptions of Britain: phonology and chronology, c.400-1200. Oxford, Blackwell.

For history, see...well, everyone back to Julius Caesar, who commented on the similarities of British language and Gaulish language. And see the somewhat dated but still quite relevant work by Nora Chadwick, which you can find online, here.

Having said that, wassailing is not Celtic at all but Anglo-Saxon. The very name, wassail, is derived from the common Anglo-Saxon toast "Waes Hael," meaning "be well."