Thank you for the comments.
I did look back at older threads, must have missed that one. Will look again, thanks. Although WHO is probably saying don't use it to replace breastfeeding? That makes sense but my son is already formula fed. I'll go and look in the forum.
The casein is what the hungry baby formula is based on , have I got that right? I read in a different thread it is the older style formula, probably what I was fed as a baby! Maybe it's more like that than first milk. I am a bit uneasy about caesin over whey.
I know toddler milk is only really about taste, I bought some once to take on holiday because I wasn't sure about the cows milk where we were going.
I am a bit unsure about why follow on can have no benefit to the baby at all. Whether there's any point if he's on first milk, I guess that's what I'm trying to work out.
Re "thickener": the caesin would make it thicker I suppose. It's not adding thickener like cornflour though!
Lots to think about, thank you everyone. :)
His anybody gone from first milk to follow on? How did you find it?