No, you're misinterpreting things. The analyzed DNA is from 5, 4 and 3 thousand years ago, at a time when there are suspected to have been no Celtic speakers in the Isles. Speakers of the Celtic branch of languages began appearing in the Isles far later than that (probably around 600 BCE).
This DNA would have not been representative of the DNA of the people who brought Celtic languages to the Isles. Similarly, the people who brought Celtic languages to the Isles are not necessarily representative of the current or even the populations contemporary to their times (minority languages can become dominant as was the case with Hungarian).
This only tells us about the population's genetics, but it doesn't link it to the Celtic language group.
This DNA would have not been representative of the DNA of the people who brought Celtic languages to the Isles. Similarly, the people who brought Celtic languages to the Isles are not necessarily representative of the current or even the populations contemporary to their times (minority languages can become dominant as was the case with Hungarian).
This only tells us about the population's genetics, but it doesn't link it to the Celtic language group.