Well Maths and Physics are definitely required and Further Maths would appeal as a vantage point (so I personally would suggest doing it).
Also if possible/offered by the college, try doing computing (ICT is just horrendous, don't opt for that, besides it doesn't give u much practical knowledge and when starting at uni, many students have no computing/programming experience beforehand).
Grades would depend on the uni, if he's aiming high like oxbridge/imperial, AAA is standard offer......but to an averagely good uni, I guess ABB is sufficient.