Medical Insurance vs Travel Insurance (Medellin)

Hi all - I wonder if one of you may be able to help me.

My girlfriend and I are moving to Colombia this November. We plan to travel the Caribbean coast for 7 weeks and then move to and settle in Medellin in January Protected content .

I have been researching different medical and travel insurance options, but coming from a country (the UK) where medical insurance is basically non-existent due to our National Health Service, some of the differences are bamboozling me slightly.

1) How necessary is access to PRIVATE health in Medellin, as an ex-pat, as opposed to the Colombian National Health Service?

2) What would getting a worldwide "travel insurance" policy not cover that getting a Medellin-based "Health insurance" policy would? Any obvious advantages or disadvantages of each?

3) As we plan on traveling for 7 weeks initially, and probably throughout our time in Colombia, would we need both anyway?

Thanks all - any tips would be very well received.

Tom