It seems that like major business corprorations, different universities place different emphasis on different titles. I agree that for the major universities in Britain ‘Chancellor’ is the correct term, but I have also known universities use ‘president’ to describe the head.
This is from a guide to the University of Oxford:
The university’s formal head is the Chancellor (currently Lord Patten of Barnes), though as with most British universities, the Chancellor is a titular figure, rather than someone involved with the day-to-day running of the university. The Chancellor is elected by the members of Convocation, a body comprising all graduates of the university, and holds office until death.
The Vice-Chancellor, currently Andrew Hamilton, is the “de facto” head of the University.
A head of a specific department of a university is commonly called a ‘Dean’