No never found the need to cage train myself either. My own experience has been when the puppy has stooped to do a wee I pick them up and take them outside, even though they may already have finished, and they have soon got the message, usually within a week there have not been any more accidents. Take puppy out as soon as it wakes up, after food, and during play, and wait until it does something, rather than just sending it outside on its own. Dont know what it is with collies though, as I have never had one that has used paper, or done anything in the night.
I would keep the puppy on the Beta food, at least for the moment, and if and when you do change, you should do it gradually, but you probably already know that.
I prefer to give half dried food with half fresh meat and vegetables for palatability. If I try to give them the meat and veg or dried food on itsown they stand and look at the bowl as if to say something is missing.
There are lots of good complete foods on the market, I personally dont think Beta is one of them, but if the dog does well on it and it suits him, that is fine. I have fed Hills for as long as I can remember, my friend feeds Royal Canin, and I know people who feed Burns, Eukanuba, or James Well beloved, so it is personal choice. Avoid Bakers as dogs seem to go loopy on it (e numbers for dogs), and Pedigree can give some dogs an upset tummy.
I also give my puppies full fat goats milk, rice pudding (not ambrosia just the cheap stuff), boiled or scrambled eggs, and cottage cheese, as having four meals a day of the same food must get boring!!
I am sure you know everything I have stated above, but its good to share experiences.