From NHS Website
Patients travelling outside the UK
• If a person is going to be abroad for over 3 months then all they are entitled to at NHS expense is a sufficient supply of regular medications to get to the destination and find an alternative supply of that medication. Patients should check on arrangements for obtaining prescribed medicines in the country they intend to visit before leaving the UK
• The NHS’s duty of care regarding prescribing ends where a patient has been absent, or intends to be away from the United Kingdom for a period of more than three months(3). Under no circumstances should the patient be issued with more than 3 months’ supply on going abroad. Further information is available on the NHS Choices website. Patients should be advised they need to check the regulations on taking medicines out of the UK and into the country they intend to visit