The UK legal position

Under the terms of the Act, it is illegal for anyone other than a RCVS-registered Veterinary Surgeon to prescribe homeopathy for animals or to diagnose or give advice based upon a diagnosis. This includes but is not limited to homeopathy, acupuncture, herbal medicine and aromatherapy.

This law applies, even if no charge is made for the service but does not apply to owners who treat their own animals. 

Exceptions are made for those supplying manipulative therapies (e.g. massage, chiropractic, osteopathy, physiotherapy), working under veterinary supervision, so long as no prescription is supplied or offered.