TLDR: When the account is frozen, it will neither receive nor make payments. When the account is closed, the bank will transfer the balance to the account you designate.
Sorry for your loss. Sadly, I too have had a lot of experience closing accounts and it does vary depending on the bank. Under £50k is usually straightforward but there was one with a £25k limit.
As per PPs, if your deceased had a business, you may need to have all the assets valued for probate before you start freezing/closing accounts.
When the account is frozen, it will neither receive nor make payments.
This happens almost instantly from when you notify them to freeze the account so check first if there are any standing orders you'll need to continue paying or regular payments coming into the account and contact those recipients or anyone sending payments to the account directly to change the payment details before you close the account. If you have password/user ID for the sole account, you can log on and scroll through, otherwise you might need to visit a branch (prob need appt for that) and bring all your doc's: DC, will, your ID, probate if relevant.
Then, make a note of the date and total balance. As per PPs, also note any interest accrued in this tax year in case you have to file a SA for your deceased.
The account will remain frozen until the bank/BS has reviewed all documents and is satisfied to close the account. Most places have a way you can show receipts of the funeral costs and be reimbursed if you need that.
The doc's required depend on each bank's policies about account balances and as per PPs, these are different at different banks.
When the account is closed, the bank will transfer the balance to the account you designate.
The main delay for transfering the money is the time it takes the bank to send the info and for the bank to review it.
When I went through this process, I found that most banks were very anxious about fraud so wanted to do most things in person and/or by post with actual documents which made the process slower. Also, at many banks, despite having bereavement teams, the clerks in the branches were generally clueless about the process so if you have to go in person, be prepared for a long afternoon of it.
If your spouse had ISAs, you can transfer these in to your ISAs beyond the standard £20k limit using APS.
Check with DWP whether you are eligible for bereavement payments if the deceased was your spouse. If so, you'll need to register at your local job centre.