At only 300w, no idea why they advise against using it with an extension lead. Probably just covering their rear-end.
You could also eat raw meat and save money by not cooking it, what's up with people, it is what it is a buffet serving station THAT is what is on offer and its price voted on, just amazes me what nonsense people come up with, what's next? could always keep it warm on an open wood fire in your dining room!
You can get 3x Crock Pots (300W each) for £34.97 from Amazon. Often super markets do slow cookers for £9.99. A bit more flexibility.
Thanks OP, bought it, absolutely no idea why but hey ho you can only be killed once (lol) and heat added as no extension lead required to reach the top of the page (y)