Thanks for all your replies!
I might give the Oat Brits a try. Semolina and 1/2 oats, 1/2 semolina might be worth a go too (thanks Cherished and Phoenix!). And I wondered about puffed wheat too, wysiwyg! DS LOVES the little bran 'worms' too, but I wondered if a whole bowl might interfere with his poo, iykwim!!!
We also do eggs, smoothies (with flaxseed, oat bran, fruit, yoghurt, probiotic, LSA etc) and pancakes etc but I was also after some other cereal ideas (for the days I don't have time to do an elaborate breakky or when he's clingy and won't let me!). He always has fruit and milk too but has gone off yoghurt atm. DS won't drink enough smoothie to make it a stand alone breakfast.