I've just looked up Starting With Pigs by Andy Case. He says a mix of 10 parts coarse wheatmeal, 8 parts barley meal, 1 part soya meal, 1 part fish meal plus minerals. Replace the fish meal with more soya meal three-quarters of the way to pork weight and then towards the end of finishing drop the soya meal back to one part and increase the barley meal by one part.
I'd be really interested to see how you get on.