What are the origins of the British?

Well, there have have been some guys lately, *cough, cough, Steven Oppenheimer, cough, cough*, that have been saying Brits actually come from Iberia and are descendants of Celticised, and later mostly Germanised, Basques. This doesn't really make sense to me, because we don't look like Basques. Personally, I think were bloody Celts, with Anglo-Saxon and Danish/ Norse imput more to the north-east. So I would greatly apreciate if someone would have some evidence (genetically researched/ historically proven/ linguistically proven) that supports my idea. It would be even better if the pre-British homeland of these people was mentioned, but the proof that were Germanic and Celtic is enough on its own. Thank you!