Why does my cat want feeding all the time?

My cat is a neutered 10 year old male, house cat. He gets fed approx. 1/3 of a tin of Whiskers cat food with with biscuits and water in the morning about 6am. Then he gets fed about 4.30pm the same amount, but by bed time approx. at 11pm he wants more? He's always looking for food and begging, he'd take the food off your plate if you allowed him to do so. I've de-wormed him but to no avail. My other cat, a female isn't like this. I have to feed her separately otherwise he would eat her food too. Is he just greedy or should I put him on 'better' dried cat food, such as Iams? Can anyone suggest anything in the U.K.? Thanks