Friends, yes, legally, with every safeguard intact: full consultation, face-to-face prescribing for toxin, consent, documentation and your own insurance in force. Immediate family, decline; objectivity and regulator expectations both point that way. Under-18s, never, it is illegal for cosmetic toxin and fillers in England.
The kitchen-table botox evening fails on three separate rules before the kettle boils: the prescriber has not consulted the patient face to face, the setting is not clinical, and the documentation will not exist. Treating a friend properly means treating them exactly like a stranger, in clinic, on the record.
Also check the course-cover point: whatever insurance applied during training ended with the course. You need your own policy before the first favour. The wider first-90-days structure, including scope discipline and supervision, is in after the certificate.