LPA or joint bank account

[Piggy Bank]

What would be the most practical option for an aging relative LPA or joint bank account.
Approximately 7 years ago we applied for LPA - financial & health,. The bank was given a copy of the LPA incase we needed to use it.
The relative now needs some assistance in dealing with their day to day financial affairs.
I am the main benifcary & executor of the relatives will.
If we add myself to the relatives bank account, I believe the total balance of the account should be used for probate but would I still be able to access the funds proir to probate being granted to pay utility bills ect while the estate is being dealt with

[Commu Comp]

As far as I'm aware an LPA ends when the person covered in the LPA is deceased and the document has to be returned back to the Court of Protection.
In our case the bank locked my deceased mothers accounts, until probate is granted.
Probate will only be granted when the HMRC have had their "cut", which wont be an issue if the estate value is below the tax threshold.
I'm going through it now, this area of "tax is taxing".
I am not a legal professional.