If you do not have an NHS number, you may be charged for your appointment with the GP and claim it back through your travel insurance, you may have to pay for your prescription.
You will have to pay for any secondary care.
For more information visit https://www.nhs.uk/NHSEngland/AboutNHSservices/doctors/Documents/Using-the-NHS-Information-for-visitors-from-abroad.pdf
GP Appointment £50
Private Prescription £15 plus prescription charge at pharmacy.