That web page (if you click the links at the bottom as well) basically relates to the Manufacture & Marketing (and therefore sale) of treatments in the hive.
It is not dealing with a beek making up their own substance (and delivery method), like that which has been used by Randy Oliver.
I have yet to read from a government endorsed source that it is illegal for a beek to treat their hives / bees with a home-made remedy, like Randy Oliver's Oxalic Acid soaked paper towels, ... or Rhubarb Leaves (which one beek in my Association swore by).
You’ve misunderstood what a “marketing authorisation” is needed for. Under the
The Veterinary Medicines Regulations 2013:
Administration of the product
8. No person may administer a veterinary medicinal product to an animal unless—
(a)the product has a marketing authorisation authorising its administration in the United Kingdom, and the administration is in accordance with that marketing authorisation; or
(b)it is administered in accordance with Schedule 4 (administration of a veterinary medicinal product outside the terms of a marketing authorisation) or Schedule 6 (exemptions for small pet animals).
Clause 2 covers the definition of veterinary medicinal products:
Definition of “veterinary medicinal product”, interpretation and scope
2.—(1) In these Regulations “veterinary medicinal product” means—
(a)any substance or combination of substances presented as having properties for treating or preventing disease in animals; or
(b)any substance or combination of substances that may be used in, or administered to, animals with a view either to restoring, correcting or modifying physiological functions by exerting a pharmacological, immunological or metabolic action, or to making a medical diagnosis.
of which part b is quite open, hence the earlier interpretation posted on this thread that if there is a marketing authorisation for a product containing the substance oxalic acid, it can be considered a vmp.
I’m not giving legal advice, come to your own interpretation by all means, but “no person may administer … to animals” doesn’t grant the “end user” any exemption from lack of marketing authorisation that you suggest.