Once again i'm not trying to be an ass about it but that question can't be replied with 100% accuracy and here's why:
1. The Brand is the legal owner of the product/brand name and brand product, but with that said, they aren't the legal owners of the domain you own, unless it's an EMD to the product, but from what i've read from the OP you added uk, us and buy to them so legally they don't own them.
2. The company may not be interested in spending the time or the money to go after you, sometimes it's not worth it for them, which once again doesn't guarantee they wont. But from this point of view, if they created registered and developed all of the above mentioned (Brand, product, etc.) they must be able to afford someone to get to you by diving you bad reviews of bad SEO for you'r domains, it's BS to do that but hey you're hurting their business too so it's kind of "payback time".
3. (This one is my personal opinion, you'll take it as you want it) You'r costumers will never be happy with you'r service, simple because you're promoting something you're not really selling, that's like selling fresh air, they will be disappointed and although you may have a few sales it will never be something that will last that much for long-term business.
4. Are you really that interested in presenting, promoting, selling or whatever a product that you don't truthfully believe in? (Once again this is my opinion) I wouldn't be able to sell something i don't believe in, surely this is Black Hat, but still would you feel good about yourself by saying to a friend or a family/relative: "hey i'm selling fake this or fake that"? I wouldn't and even if you don't explain it to everyone someone will notice you'r involved in the long run (simply because you'r competing with companies that may have the money to do it)
Hope I've been clear with my point and that this has helped the way you'r thinking, i'm not saying for you don't go trough with it (if you really want it you can) but I don't advise you to do it as most of the members here already explained.
Cheers