DH was very difficult to insure, (cancer and a stroke) , and it cost an arm and a leg - Staysure wanted over £2000 for a two week cruise. MIA are very good, £350 joint insurance for the same cruise.
Eventually a friend put us onto a civil service insurance company, (DH was a retired civil servant).
You need to join the Civil Servants Pensioners Alliance, only open to retired civil servants, and then you have access to their wonderful insurance - no medical screening, you just need to be fit to travel. It used to be under £300 a year, joint annual insurance, renews automatically every year.
DH died in February, and luckily, it is still open to me, so I have renewed as a single.