When my husband developed advanced prostate cancer (a cancer that would kill him) it became difficult to get travel insurance. Nationwide BS saved the day for us - we opened a FlexPlus current account (you don't need to make it your main current account), which includes a package of various benefits including worldwide travel insurance. I think it costs £13 a month. OH had to declare his condition, of course, and answer various questions, but they only seemed concerned about how many drugs he was taking for the cancer. After the screening they said they'd have to charge him an extra £80 or so, but that still worked out quite reasonably for us. You can check out the medical screening before you open the account, and you only need ton keep it as long as the insurance is useful to you.
We chose not to go outside Europe just in case there were complications, but everything worked out
fine and we had several enjoyable, precious holidays together during his final two years.