Suddenly waking for milk?

My son is nearly 6m and has slept through from approx 4m until about 2 weeks ago. He is now weaning and on 3 meals a day (porridge for breakfast, puree veg at dinner with fruit and a yoghurt and the same for tea). He goes down at 8pm and I give him a biottle at 10. Sometimes he takes it, other times he doesnt. Following advice of another member, when he was fussing at 4am last night (the wakes are usually between 3-4) I gave him a bottle and he had the full 6oz but wouldnt take the bottle I offered at 10. He has his tea at approx 6/630 as we dont get home til about 545.

Can anyone offer any advice on what we could do/change to see if it will help him sleep through once more?