Apparently getting travel insurance is just not possible when referred and sitting on a waiting list for an outpatient appointment (for symptoms that have not been formally diagnosed). It’s just not possible to insure someone when they are awaiting diagnosis. Any policy claim would be void as you’re not covered in the first place.
But with the length of NHS waiting lists, often a year or more, what do people do? Not go on any foreign holidays for a couple of years until they have a diagnosis? Cancel anything that’s already booked? Do people just assume that they don’t yet have a diagnosis so there’s nothing to declare, and go on holiday anyway?