Re: Re: NHS treatment in UK (Mailbag Friday, 30 March 2012) Free entitlement to NHS treatment has nothing to do with citizenship nor NI Contributions. Like it or not. Apart from genuine emergencies occurring after arrival in the UK, entitlement depends on your normal place of residence, and assuming you are entitled to reside in the UK. Absences of 3 months are permissible.
See http://www.adviceguide.org.uk/england /healthcare_e/healthcare_help_with_health_costs_e /nhs_charges_for_people_from_abroad.htm