UK Landlord Forum / Life

So here's my situation:

I posted a Section 8 notice on Monday using using Evri Postable Next Day. I was hoping it will be delivered today (Wednesday 22nd June) at the latest. Alas, it looks like it will be arriving tomorrow.

In the notice, after citing Ground 1, I put down "The court proceedings will begin no earlier than 23 August 2022". If the notice arrives on 23rd June, is my notice invalid?

The reason for my confusion is that I'm not sure if  you can begin proceedings on the last day of the notice period, or do you have to wait until that day has finished.
(A confusion not helped by the fact that an old version of "Form 3" says: "The court proceedings will not begin until after xxx (Give the earliest date on which court proceedings can be brought)" <--- self-contradictory?)

There's also a break clause in the tenancy agreement, where I have to give two months' notice. Does my Section 8 automatically trigger that, insomuch as I don't have to wait till the end of the fixed term to use Ground 1?