Someone I spoke to who isn't a bank employee did suggest the banks may not want to disclose specifics regards dates etc, particularly if it's a prevention of money laundering - otherwise those who engaging in laundering would simply work the system.

Just supposition.

It is a long time since I paid into my main affected account via PO or ATM, but it continues to be rejected (tried recently). I have paid in over the counter whenever near a bank branch. I am wondering it it is £10k paid in anyway eg once you have paid in 10K even if all is over the counter in a branch, you simply cannot pay in at the PO.

It doesn’t matter whether you pay in via post office or bank. It’s the annual limit you can pay in, in cash to your account.
Limits vary.
NatWest is 24k
Santander is 10k

I gave two accounts with NatWest and the 24k limit is across BOTH accounts (so I can’t pay in 48k).

You can electronically transfer cash between banks as this doesn’t count towards the annual limits.

You either have to have several personal accounts and do electronic transfers once you’ve reached your pay in limit or open a business account.

Oh that’s strange, Mirror as not what my bank have told me.

Some banks haven’t introduced limits yet, I believe.

NatWest have made it clear that they won’t accept more than 24k paid in, in cash on a personal account.

Bloody banks!

I’ve messaged you x

Tried to reply but I got a message saying 'User 'KirstyKiss' has blocked your personal message'.

I had a letter last week from my Co Op bank to say anything beyond 10k cash at a post office in a financial year must be paid in at an actual Co Op bank branch..