@ Regulus: the main problem with Bell-Beaker that I see is that it also extends into clearly non-Celtic areas (in particular southern Scandinavia and Italy). The case for Beaker-Bell being associated with some kind of common 'western' branch of IE (from which Common Celtic, Common Italic and Lusitanian evolved, as well as which heavily contributed to Germanic) is way better than the case that for Beaker-Bell being Celtic, in my opinion.
@ Cambria Red: Regarding the 'Celtic' area in Iberia, while I agree on the rough size, I would say that 'Celtic' is a slight misnomer, and I would further suggest to very roughly break it down into four sub-regions (which are also somewhat anachronistically) to explain what we are actually talking about:
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Central Area: apparently Celtic-speaking without other influences (though I'm uncertain about the Cantabrians?

), with exception of what I would dubb "Celtiberia proper": it was culturally influenced by the Iberians (including writing system and cremation).
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Gallaecia: Celtic-speaking over an earlier Lusitanian substrate (including Lusitanian deities and mixed Celtic-Lusitanian typonomy).
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Tejo area: The Lusitanian-speaking area.
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Post-Tartessian region (Algarve, Guadiana river and Guadalquivir river areas): even if we assume that this region was previously non-Celtic (ie, Tartessian as a non-IE language), it is clear that the region must have been heavily settled by Celtic-speaking peoples between the 5th and 1st century BC.