Is there was ever any doubt they've now changed/clarified the T&C's to confirm that ALL EPP and student purchases get the cashback. Pic below. See their FAQS on the claim page.
So it's £364 through TOTUM / UNIDAYS / Student Beans / Perks at work etc
Trade in ANY broken smart watch for £100 (a £6 Amazon one will do. I've successfully used these 3 times before).
Claim £100 cash back using current Xmas promo here -
https://2021.samsungpromotions.claims/20_days_of_christmas/en-GB
= £164
https://2021.samsungpromotions.claims/20_days_of_christmas/en-GB