He already feeds the sheep on the fields with hay (in one of those hay holders) and I know that's not allowed with Countryside Stewardship.
Not necessarily true as a general rule, although of course I don’t have sight of your specific agreement.
I have farmed under Countryside Stewardship and three other more recent environmental Stewardship schemes.
Different rules apply to different grades of land, and you can choose different options for most fields and areas to achieve the optimimum environmental benefit and compensatory income for the particular farm and farmer. Most except the very most rigorous options allow hay feeders which move and are moved. But of course you may have chosen “HL6” or whatever is the highest level of environmental care in your scheme, which may indeed stipulate no feeders of any kind.
Silage is generally not to be fed on grass, or if it is then the feeder must be moved for every bale. They often do allow a static feeder if there is some hard ground it can be on.
The CS scheme I was on ten years ago did allow us to use purpose built wooden feeders for big bales of silage on extremely environmentally sensitive moorland, which we moved for each bale (so every three to four days.)
Some options allow only hay which is fed by hand and fluffed out so it doesn’t sit on the ground, but a hay heck for sheep which is moved every day or two is allowed under many options, as is a ring feeder for a big bale of hay, again if it is moved for each bale.
I’m not sure where you are but in Cumbria they were latterly only putting effort into actively monitoring Higher Level schemes - but of course they would follow up on any input they got, and their field staff travel widely in the course of their work, so might just happen to spot something as they passed by.
If you were found to be in breach, you could be made to repay all your payments under the scheme for the entire length of the scheme, so it’s definitly worth making sure you comply!
In general, the field staff were extremely helpful, and most know a reasonable amount about farming, so you might find they could suggest how you might pass on the requirements in your grazing licence in a way that makes sense to your grazier
I’d advise you to get out your agreement and see what payment dates and amounts are in it, put them in all the calendars you have and a copy in a fireproof safe too, and start chasing them immediately and robustly for any payment which is late. The Rural Payments Agency is a disgrace.