Rewards

Ben now has a sticker chart in the bathroom. He gets some sparkly stickers as rewards when he uses the potty. He likes the stickers, is pretty pleased to get one, but it's just not working as an incentive to 'go'.
He has no problems using the potty. For a while he was even happy to take his nappy off and go on his own when he needed to but now he can't really be bothered. He will go when we make him before/after bed and before going out but the rest of the time he just says he doesn't need to and uses his nappy. He doesn't even tell us when he has a wet nappy.
There must be a way to make him want to get out of nappies and use the potty full time but we haven't found it yet.
He wont wear nappy pants or pull ups either.