I've not checked that the supplier who has the rated fills can supply a DoC certificate, I'll ask them. I doubt anyone is bothered about complying in any large number as otherwise the supplier, who does labels, would no doubt stock them.
I think that this part of the BS will be more ignored than any other realistically - I've seen no drop off in the sale of generic spare parts either such as universal O-rings, cheap copies of OK pins, etc.
Kurnal - in essence the standard is saying only genuine manufacturer's parts & refill agents can be used unless an alternative has been verified as not affecting performance and is accompanied by a Declaration of Conformity by the supplier or manufacturer of the component.
Stickers have to be applied where non OEM parts have been used.
Taken to the daft extreme you could end up with a vast array of identical parts on your van if you had to stick to OEM (especially if they brand them).