My prescriptions are sent to Tesco, if they don’t have all my meds, ( sandrena) they send a text asking me to ring, when I do there is the option of a “bar code” for my whole prescription ( prescriptions cannot be split). I can then contact other pharmacies to ask if they have it, and give them my bar code over the phone so they can allocate it to me immediately. If you know boots have it, you can just ask your pharmacist for the bar code