You don't have to be potentially professional standard to get an organ
scholarship at Oxford or Cambridge (I was involved with various college
choirs in both places from 1980 till a decade or so ago and still have
some contact with some of them, as well as knowing a lot of former organ
scholars).  Just about all of them have the ARCO diploma but only a
minority have the FRCO while they are at university.  You need to know
which college they were at as some rank far above others.  Anyone who
was organ scholar at somewhere like King's College Cambridge or Christ
Church, Oxford ought to be good enough to get a cathedral job later on;
but former organ scholars at some of the less musically prestigious
colleges (I would count Balliol among these) are likely to find a career
doing something other than playing the organ, though possibly still
within music such as teaching or publishing.  Cambridge organ scholarships
are more sought after than Oxford ones in general, because Cambridge
colleges put more money into their music and this results in better
instruments to play on and more foreign tours, recordings, broadcasts
etc.

Virginia Knight
Personal homepage: http://www.ilrt.bris.ac.uk/~ggvhk/virginia.html