I was lucky enough to miss the worst of this during my "time", having only experienced it for a few days on a visit to Halton last year.
As I had visited Halton a few months before PAYD had been introduced, then a few months afterwards, the differences were stark, and quite depressing.
iirc a cup of tea was/is included in the core breakfast menu, as was a slice of toast (but butter/jam was not). From the normal "Full English" you could select only 5 items, and they were broken down further into more specific food groups. The "hostess" commented one morning that I was only allowed to have "3 carbohydrates" on my plate, so I would have to pay for one of my 2 sausages or a piece of bacon!
As mine was only a classroom based course, it was no real hardship for me, however the guys doing the physical stuff may have struggled on such meagre portions. Yes, I am sure the meal did meat the required calorific value as determined under the governments recommended daily intake for an average male. However, take into account all the extra activity military students, or even average squaddies do on a daily basis, and I'll bet a pound to a penny it falls short.
Combine that with the fact that civilianisation. IT always used to be if you had a bad meal, there was banter to be given to the cooks by the "lads", so there was some incentive to buy good produce. Now the only incentive is profit margins, and all the cooks go home and have no interaction with the "lads" at all.
In my mind, not the best move ever made. I'm glad I'm out.