I think Les and Keith and the Salt Town Poets were scheduled for Sunday morning because they appeal to the more cerebral and intellectual type of person - the type of person who does not, to use a vulgar expression, get rat-arsed on Saturday night and lie late abed on Sunday groaning 'Oh My God, never again'.
Such persons spend Saturday evening sipping mineral water, and reading the works of Proust in order to prepare themselves mentally for the literary and comedic feast to come on Sunday morning.
Another, and more prosaic, explanation may be that Keith had to get away early to travel home and dear old Les, hard worked as ever by festival organisers, had a couple of hours to fill in before appearing on the main stage.
Whatever, they were brilliant.
Looks like the Festival Club Stage was one of the festival organisers better ideas.