I think I'd look at his food intake in the day and try to balance out the food groups a bit. If he is not so interested in the bottles it could be that he is too full from solids or that he feels his dairy intake is complete with the solids he is getting (yoghurt, milk on wheetabix and the few oz of milk he accepts) but finds himself hungry in the night.
Couple of things I'd try:
- drop the middle of the day time bottles altogether so he is more inclined to take milk prior to BT which will see him through the night better than his dinner and only a little BT milk (so focus on morning WU and BT bottles only)
- switch the yoghurt snacks for other food groups, veg, fruit, protein (whilst yoghurt is a great dairy solid it doesn’t provide the same level of nutrients as formula which might be adding to his night hunger)
- bring dinner solids much earlier, whilst it may not fit in with a 'normal' evening meal time many people find an earlier last meal works well, LO eats more and is also more inclined to take a better milk feed at BT (I'd bring dinner to more like 4pm). Most LOs tend to take in calories earlier in the day more so than in the afternoon/evening so I'd look at getting veg and protein into breakfast/snacks/lunch and focus less so on the evening meal. A smaller evening meal could also help to increase the BT bottle.
- look at how much carbsy food LO is taking and possibly switch some of these to other food groups. LOs do need several carbs portions per day (more than we might imagine) but perhaps he is full from the carbs groups, wheetabix, bread and butter. Perhaps you can offer an egg for instance at lunch time, or some meat or beans and cut back a little on the bread?
- Not sure what sort of purees you are giving at the evening meal, maybe switch to finger foods? Less may go in but again that would give more chance of LO being hungry for the BT milk. The aim of course being to get that night time milk need fulfilled in the day instead of at night.
- offer water at night instead of milk
- as pp said pick a plan and stick to it. PUPD is fine if it suits you. I tend to go for more of a gradual wean method so I'd cut the night milk by half immediately then offer only water (do this say 2 nights) then reduce night milk by another oz (another 2 nights) then reduce another oz (2 more nights) then offer water only.
hope something here might help