Yes. If an MD places an order for snake oil to Advent they can make it (assuming they have the ability to properly process snake oil to GMP standards).
From what I see, most common "Specials" are formulations with the same active agent but different "mixers". Sometimes different doses.
What is most interesting is 1.6 on page 3. Specials does NOT apply to:
1.6 The exemption and this guidance does not apply to other unlicensed medicinal products, for example: . unlicensed herbal remedies supplied under regulation 3(6) of the Human Medicines Regulations 2012; . unlicensed homoeopathic medicines (prepared in a pharmacy); . investigational medicinal products; . intermediate products intended for further processing by an authorised manufacturer; . medicinal products for export to countries outside of the European Economic Area; . products prepared in a pharmacy under regulation 4 of the Human Medicines Regulation 2012.
OK, good to see that herbal and homeopathic snake oil is excluded. The third clause is interesting.