I have a 21 year old son, who went away to university last year. This year he has decided to move back home to study. He gets £9K a year maintenance grant - last year his student accommodation ate about £5K of that. We think it is fair that he contributes to the household finances, as obviously our bills etc go up when he is home. And frankly, it would be a great help to us. What sort of sum do people think would be reasonable for bed and board?