I'm in a situation for the first time ever where I need to keep taking a particular medicine, it requires a prescription, but there seems to be no information about how to manage the logistics of it?
Do I have to book an appointment with the GP every time?
Or is there some way they can say "yo just let billysielu get this medicine whenever he wants"?
Yes it is a repeat prescription as people above have mentioned - though what they don't seem to have mentioned is that you need it to be recorded as such. Does your GP surgery use an online booking system at all (there are a few companies providing this service for the NHS and various surgeries use them now)?
If so then you can register with your GP receptionist and go onto say the patient access website - under your medications you'll have a section for your repeat medications - if it is under there. (the receptionists will be able to tell you this if/when you go to register too) then you can just request the repeat online - if you use electronic prescriptions too then it should just get sent straight through to your pharmacist.
Also - if you have/had a paper prescription for the medication then does it have the medication printed on the part you kept - i.e. you can tick the box and put that into a box in your GP reception to request a repeat?
Is this something that you've had as a one off but some consultant has requested you be prescribed regularly - your GP ought to just do so but you could always mention it at your next appointment or again just pop into speak with reception at a less busy time and just as them to check on the system for you and/or sign up for the online service as mentioned already.
Lastly - how frequently are you going to get the medication - every month? every 2 months? - Is it more that one form of medication? Take a look at what your prescription charges will be and then figure out if it is worth getting yourself a pre-payment certificate - this could work out cheaper for you - you can just pay for the whole year in advance:
https://www.nhsbsa.nhs.uk/help-nhs-prescription-costs/prescription-prepayment-certificates-ppcs