If you live in the UK for more than 6 months of the year you are a UK resident and not an expatriate, so you are ineligible for many international health insurances. Many international insurances are designed to cover a wide range of medical treatments, with the proviso that for serious problems the person will be repatriated to the UK for treatment.
Even when cover applies in several countries, most insurers will only pay the treatment costs if equivalent treatment is not available in the country you are in. Few insurers will pay the travel costs.
Policies are designed to cover people from one country who are working in another country or living there as an expatriate. Most cover treatment in the country the person is in, treatment elsewhere if that is a better medical solution, emergency treatment almost anywhere and repatriation to their home country.
There is a huge difference between covering unexpected treatment overseas, and covering deliberately sought treatment.
Policies that appear to give the option of treatment in any country may effectively not cover medical travel by excluding cosmetic, dental and most elective treatments.
Policies may also exclude it by limiting treatment only to approved overseas hospitals, so not paying for treatment in the country or clinic the customer chooses.
There are one or two reputable international health insurance policies around which will cover people worldwide. These are mostly aimed at the international jet set with homes in many countries who travel around a lot on business and pleasure. They offer very wide cover but are very expensive.
Other so-called international health insurance policies are offered by companies where the insurer does not have a UK licence. Some may be reputable, but as a consumer you have no one to complain to or any legal rights if something goers wrong.
Other so called international health insurance policies from companies where the insurer does not have a UK licence are not reliable. Some offshore companies have a reputation for not paying claims, and a limited adherence to rules, regulations and the law.