Thomas Cook
Thomas Cook, which is one of Britain's best known tour operators, and is a public limited company - listed on the London Stock Exchange.
Thomas Cook offers travel insurance through comparison sites, whilst its direct products are offered through Roam. Their policies are underwritten by Great Lakes Insurance SE.
Because the insurer is based in Ireland, you won't have recourse to the UK Financial Ombudsman Service if you want to escalate a complaint against it.
An industry average has been used for its complaints score, as the data does not show up in the Irish Financial Ombudsman, and it didn't provide this data directly.