True, but he's still entitled to a notice period if he has been dismissed. That is one of the differences between dismissal for (whatever reason the employer decided) and dismissal for gross misconduct (where the employee has fundamentally breached the contract - as per Ethel above).
Unless he's a casual worker, when he's employed on an hour by hour basis. That's what we are trying to sort out here.
If he's being paid weekly, gets a pay slip with his NI number on it (even though I realise he probably doesn't earn enough for there to be any deductions), has been there 2 months and is working those hours regularly, I reckon he should argue that he was on a week's notice.
If, however, the employer tells him which hours he will work and it varies, he probably can't argue legally for any more pay than the shift when he was sent home.