Available to almost any individual. Most can be extended to include partners. Some automatically include children. They are usually 24/7 and either worldwide or for UK only accidents.
As general products they do tend to have a longish list of excluded activities, so cover may not suit you .A general policy may look cheap but be of little use to you if your hobbies are motorcycling, mountaineering and diving.
What many also have, and you will rarely see this in print, is a hidden variable list of occupations, locations, ages and other factors. Those that are individually underwritten will only quote for you if they think you are a good risk. Underwriters are under no obligation to give you reasons for refusing to cover you.