Hi Zed
Really sorry to hear the way this has panned out.
I’m not a lawyer, but MrsJulianA is an HR Manager and she makes the following points:
If a letter is sent recorded delivery the intended recipient can refuse the letter and it is then ‘not delivered’. A tribunal will assume that a letter posted by ordinary mail to an address which is reasonably believed to be the last known address of the intended recipient will be delivered two days later.
The basic award for Unfair Dismissal is £10,500 and the Compensatory Award for Unfair Dismissal is now up to £66,200 depending on age, how hard you have tried to find another job and factors like that.
She also suggests that you get legal advice on this, but I think you have that base covered already.
Good luck and let us know the outcome of this and of your interview!