Hi Pepperminty, attached link/extract from MHRA document dated 2014 refers to "named patient" prescribing. I haven't read it all & don't know whether there is anything more up to date.
https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/373505/The_supply_of_unlicensed_medicinal_products__specials_.pdf"The supply of unlicensed medicinal products (“specials”) MHRA Guidance Note 14
2.2 An unlicensed medicinal product may only be supplied in order to meet the special
needs of an individual patient. An unlicensed medicinal product should not be supplied
where an equivalent licensed medicinal product can meet the special needs of the
patient. Responsibility for deciding whether an individual patient has “special needs”
which a licensed product cannot meet should be a matter for the doctor, dentist, nurse
independent prescriber, pharmacist independent prescriber or supplementary prescriber
responsible for the patient’s care. Examples of “special needs” include an intolerance
or allergy to a particular ingredient, or an inability to ingest solid oral dosage forms.
These examples are not exhaustive."
Off at a tangent from your original post but hopefully relevant to your question as to conditions under which "specials" can be prescribed.
Wx