OP I hope we haven't scared you away!
I found this explanation on the NHS website:
^If you move to England permanently or return to live in England permanently, you're entitled to free NHS hospital treatment. Like other UK residents, you'll have to pay some NHS charges (for example, for prescriptions), unless you are exempt from these.
If you move to the UK, you will not be charged for NHS hospital treatment from the date that you arrive as long as:
you intend to live permanently in the UK, and
you have the right to live permanently in the UK or have a "route to settlement" that will allow permanent residence in due course
You'll be expected to prove that you meet these requirements.
Your spouse or civil partner and children under the age of 16 (under 19 if in full-time education) are also exempt from these charges if they live with you permanently.
If you're not entitled to live in the UK permanently but you've applied to the Home Office to enter or stay, you'll be charged for hospital treatment until:
your application is granted, or
you have 12 months' lawful residence in the UK^
I think what you need to check is whether the Tier 2 visa is still automatically considered a 'route to settlement' visa -- it used to be, but I believe they have made some changes to it in recent years which means you can only apply for permanent residence after some years if you also have a certain minimum salary.