The ecclesiastical court system was a complex hierarchy with the senior courts (excluding appeal courts) being the Archbishops' Courts. The country was divided into two provinces - Canterbury and York - each presided over by an Archbishop. The Archbishop of Canterbury was senior.
The Prerogative Court of Canterbury (PCC) had jurisdiction over the province which covered the south of England and Wales, or when the deceased held property in both provinces, or those resident anywhere in England or Wales who died abroad.
The Prerogative Court of York (PCY) had jurisdiction over the province of York covering the north of England.
The location of the deceased’s property usually determined where the will was proved. Most probate matters were dealt with at a more local level by the Archdeacons' or Bishops' courts or the peculiars. Some nonconformists and those who held land in more than one archdeaconry in different diocese had the will proved in the Prerogative Courts of Canterbury or York. The Phillimore Atlas and Index of Parish Registers displays county maps showing the ecclesiastical jurisdictions for each parish.
As a rule of thumb therefore...
Where land and property are all in one archdeaconry, wills were proved in the archdeaconry court.
Where land and property are in more than one archdeaconry but within one diocese, wills were proved in Bishops' Courts - either consistory and/or commissary.
Where land and property are in more than one diocese but all in Province of York, wills were proved in the Prerogative Court of York.
Where land and property are in more than one diocese but all in Province of Canterbury, wills were proved in the Prerogative Court of Canterbury.
Where land and property are in both provinces, wills were always proved in the Prerogative Court of Canterbury.
Where land and property was held outside an archdeaconry but in a peculiar, the wills were proved in the peculiar court.
Province of York wills are held at the Borthwick Institute and the Province of Canterbury wills are held at The National Archives
Courts such as the Court of the Dean and Chapter often acted on the bishop’s behalf in probate matters, so records for such cases are usually filed in the records of this court as opposed to Bishops' courts.
It is thought that up to 1857, because of the complex tenures, only ten or twelve per cent of the population held sufficient property to warrant probate. So don’t assume that all your deceased ancestors left a registered will.