Wages not paid on leaving job?

My husband worked part time as school bus driver. No retainer paid in the holidays. He is only paid by the hour, no sick pay. The company paid him a weeks hol pay at christmas and he would have got two more in the summer break. He joined in October, He was not given a contract or a letter with details of hours, wages, notice, sickness or holidays. He left last week giving 3 days notice and the company say they will not pay him for his final weeks work as they paid him holiday at Christmas, Can they do this please?