I believe Eurotunnel will cover everyone, including existing conditions, I use it for taking my FiL away, as he has a list of ailments that go to a 2nd page. All I have to have is a letter from his Dr saying he is ok to travel.
My current account has worldwide insurance, and I do not pay extra for my declared conditions
Eurotunnel sound worth a look thanks for heads up. I got a quote from staysure online then a day later got an email offering a 15℅ reduction so might be worth frosting if signing with them.