Even if Israel responds, USA and Britain will not because then their bases will be the target of Iranian missiles, just like what happens in Ukraine were they don't participate by themselves in attacks against Russia. So if Israel wants to make attacks by itself and then be the target of massive Iranian attacks, that's a scenario that Iran might like...
“Israeli Minister of Defense Yoav Gallant told Defense Secretary Lloyd Austin Sunday that Israel has no choice but to respond to the unprecedented missile and drone attack launched by Iran over the weekend"
https://www.caitlinjohnst.one/p/israels-latest-lie-is-that-it-has
Discussion
Let's hope that cooler heads in Israel prevail. I read that the generals in Israel clearly told the politicians that this has to stop. No more escalation because they can't defend against attacks like this. But I can't confirm this. It was one of these reports where anonymous sources told something to a reporter. But I think that USAUK will tell them the same. As you said, they are aware of the threat.