The Designated Prescribing Practitioner must be an experienced prescriber willing to supervise your course in practice, and finding one outside an NHS team is the hardest part of the V300 for aesthetics nurses. Routes: your existing aesthetics prescriber, prescribing-mentor services, or arranging NHS practice hours alongside. Confirm your university accepts the arrangement first.
Universities require a DPP and a practice environment for supervised prescribing hours, which self-employed aesthetics nurses do not automatically have. The workable answers, roughly in order: the prescriber you already work with agrees to act as DPP; a paid DPP-matching or mentor service (they exist, vet them like any provider); or keeping one NHS day a week during the course, which solves the environment question too.
Ask the university two questions before paying anyone: whether they accept an aesthetics practice environment, and what they require of the DPP. Answers vary between institutions more than the marketing suggests. More in the prescriber guide.