NHS covers everything for everyone irrespective of nationality as long as you have a legal permission to live in UK for short and long durations other that a tourist visa.
Secondly, I had very bad experiences twice with different overseas medical insurance policies taken from India. Deductible is too high and in many cases process is not straightforward as you have to pay the money upfront for treatment whereas an insurance taken in foreign country is quite streamlined where it is a routine matter between concerned hospitals and insurance providers. The only precaution to take while taking these policies is to make sure what is covered and what's not.
This article is definitely more of an advertorial than anything else.
