Hello there! This hypothesis seems unprovable in that archaeologists have yet to uncover any physical evidence of a Phoenician presence on the British Isles. The only evidence that Phoenicians even made it there at all comes from Avienus' fourth-century A.D. poem Ora Maritima, which describes a Carthaginian expedition in Northern Europe under a certain Himilco (probably around the early-fifth century B.C.), while Pliny the Elder mentions the same expedition without specifically mentioning Britain. In their defense, however, both authors drew upon earlier sources that may have ultimately derived from the original Carthaginian reports. Scholars have then extrapolated that the Phoenicians (and, before them, the Tartessians) acquired their tin in or around Britain, the elusive "Tin Isles" of antiquity. But this does not necessarily mean that the Phoenicians introduced the domestic cat to the region; nor is there any specific evidence, as far as I'm aware, that either the Phoenicians/Carthaginians ever kept domestic cats. If someone knows otherwise, please correct me! :)