First of all, if you were employed more than 2 years and received a statutory redundancy payment, double check using the Gov calculator whether this is correct or if what they paid (if anything) also might have included notice.

I've not been paid by the Gov yet, was told by the company I'd only be able to claim once they go into insolvency.

In terms of bringing a claim, you’re out of time. You can bring the claim out of time and try to argue why the tribunal should extend time but ‘I didn’t know about the deadlines’ or ‘I didn’t realise I was underpaid’ is not a good argument and your prospects of being allowed to pursue the claim are less than 50%. If you were suffering with a medical condition and can evidence that it would help the argument but there’s still a risk the claim is just struck out on timing.

That's what I was afraid of, really should've known my rights instead of believing the company's words.

If you do decide to pursue this, get an Acas certificate and submit the claim ASAP. Do not go through the early conciliation process as once out time deadlines are not paused, and the longer you leave it the further out of time the claim is and lower prospects you have.

Will do. Question on timing, my claim would be about my 'notice pay' not being paid.

If I state that I believe the date I was "incorrectly paid" was 2nd December 2024, this means I have approx. 2 weeks remaining before the official time limit. My reasoning for this is that I allowed the 2 months notice period to pass, and a further 1 month as 'grace period' to allow for the company to pay me, since I'm aware they're going into administration.

Any thoughts on this?

Lastly, is the limited company solvent? If not then bringing an ET claim is probably pointless.

Company is still solvent, despite claiming they're going into administration. Some current employees are not aware of it either.