Hypothetical Question

Let us suppose that after the next election Labour swings far further to the left than anyone sane would predict and in the process becomes strongly anti-E.U (a hilariously improbable scenario, I know. But stay with me here). Let us suppose that the party's new anti-European stance placed it at odds with the other parties in the S&D group. Let us suppose that Labour were then to pull out of S&D and join the EUL-NGL group... along with unrepentant Leninist parties such as the KKE, the KSČM, the PCF and the PCP, along with the likes of Die Linke and along with Sinn Fein. Now then. What, exactly, would the reaction from the Tories and the right-wing media be like?