I think there’s two separate issues here:
1 what can you do about the dismissal, which is the question you asked in the OP? Legally, nothing, as I said above. However, depending on the answers to the questions about probationary period, and on what legal method they have used to dismiss you...
Ok - firstly, I’m very sorry for your situation, and for your partner’s too.
You say “laid off”. That term is usually used to describe redundancy, which is not your situation. Your situation is “dismissal”. The fact that you’ve had no warning would imply you’ve been dismissed for gross...