OK, lifted from the Breeders' Code of Ethics on the GCCF website:
"The GCCF strongly recommends that no kitten should be permitted to go to a new home before 13 weeks of age. At least seven days prior to this, the kitten should have completed a full course of vaccinations, including a health check, given by a Veterinary Surgeon or by a listed Veterinary Nurse under the direction of a Veterinary Surgeon. The breeder should ensure that kittens are house-trained, inoculated and in good general health."
No idea what the other governing bodies in the UK say, but I would imagine that it'd be something along similar lines. If the breeder is registered with GCCF, TICA or FB, then selling kittens that young will land them in some serious hot water.
Unfortunately, this does not apply to unregulated breeders who are free to get away with just about anything. And the trouble is, where you have popular breeds and a potential buck to be made, there the unregulated breeders abound. All they care about is a fast turnaround of cats and kittens and the money they make, especially where demand outstrips supply. Any breeder worth their salt will actually only be braking even with each kitten or even make a loss, once you account for stud fees, blood tests, paperwork, food, vaccs, chipping etc.
Sheryl, if you are looking to acquire a Bengal (or any breed of pedigree cat for that matter) your best bet is to go through the relevant breed clubs who will point you to their kitten list and a reputable breeder.