I think you may be misunderstanding the entry in the probate calendar which states that probate was granted to the Public Trustee. The calendars give the name of the person (or persons) to whom the grant of representation (either probate or administration) is granted in order that they may administer the deceased person's estate (i.e. bringing together all their assets and distributing them appropriately). The calendars do not name the beneficiaries of the estate (i.e. the person or persons to whom the estate was left or who are entitled to all or a share of it in the absence of a will).
The Public Trustee is, effectively, the "executor/administrator of last resort". He becomes involved if a will does not appoint executors (or if the executors named are dead or unwilling to act) and there is no appropriate living person who can or will accept the responsibility of administering the estate.
The actual grant of probate, which you can get from the Probate Service for £6.00, might give you more information. Details of how to send off for it are given at http://www.justice.gov.uk/courts/probate/copies-of-grants-wi...
Hope this helps