It is obvious you are sorting out the affairs of dead person ( sorry for the loss ) who has died intestate.
You should freeze the accounts and you do that by showing the bank ngr a death certificate. Nothing can go in and go out after that. The other grasping relation may wish to dip into it but they cant do that ( xc for funeral expenses)
and then you make your way thro' the list of duties of something like this
http://death-duties.co.uk/content/executors-and-administrators
[ One of my tenants paid me rent post mortem by DD and I had to give hell to the rather gormless kids who couldnt bring themselves to freeze the dead father's account. I thought it was probably unlawful for me to accept a payment from someone I knew was dead. ]