Will my cats ever be friends?

I have a cat called Colin who is 2 years old now, in May I got Ben - everyone said that once you get his little ballies cut off they would just get on...... but since day one, well they were ok at first and even sat together on the chair at times, although it took Colin until last month to forgive me as he has only just started jumping up on my lap again, however, Ben just wont leave him alone! When Colin comes in Ben jumps on him straight away, Colin tries to ignore him but eventually he fights back and is constantly growling (Ben doesnt growl) I have tried to leave them to get on with it, and I've tried to tell Ben off too but neither work! What can I do? I love them both - I got Ben because Colin was far too independent and I wanted a Cat I could train to stay in more, which Ben does (although he goes out for about 5 hours a day) and he is soooo attentive to me, but it would be nice if they could be friends, or even just ignore each other! Long question I know, but I thought I'd ask the experts! xx