Great question — answering as the UphillTech team:
So-called travel health insurance is not required when you're "travelling around" but rather when you are in a place that doesn't provide free health care to you because you are not (yet) a resident. For example, a (now) Canadian Permanent Resident in my family had travel health insurance from first landing in Canada until becoming covered by OHIP . The wise thing to do would be to buy coverage for the trip from UK to Canada and the first 3 months in Canada. Then after 6 months of not needing coverage, buy coverage for the trip back. You will want to be sure you have health coverage when you are in the US, and you might want the sort of cancellation/delay coverage some travel insurance...
Full answer by Kate Gregory: https://travel.stackexchange.com/a/198456 (CC BY-SA 4.0).
Need it done for your business? UphillTech.