I hope that the Signal leak pushes the Government further towards the EU.
Vance is far more interested in cosying up to Middle Eastern leaders, Turkey etc and clearly has a strong antipathy towards Europe. All that money laundering and tax legislation getting in their way...
I imagine he also fancies himself as POTUS on the next ticket. So potentially this may signal(!) a long term break.
Any deal made with Trump - however unlikely that seems - would be undermined by Vance at every turn and he does appear to wield significantly more influence than Pence ever did.
I assume the Government is also re-evaluating what security information they can safely share with the US administration. They are chatting on unsecure networks. We must assume Russia is listening in.
I would hope that the Labour government also learnt from previous Conservative cockups regarding use of WAs (I bet they haven't).