The cease & desist mentions Asda [1] and [2] says "Asda chose NielsenIQ Brandbank, their existing digital content provider for 13 years"

So I'd wager the C&D came from Brandbank - who presumably supply product photos and product data (barcode, pack size, and all the other data like nutritional information you'd find on the packet if you were browsing in store)

[1] https://www.trolley.co.uk/imgs/cease-and-desist-letter.png [2] https://www.brandbank.com/asda-accelerates-their-rich-conten...