Welcome to Cancer Chat. It is always difficult to get insurance with a cancer diagnosis, particularly if you are still undergoing treatment. I have even had difficulty in getting travel insurance.
If you use the search engine on the blue banner at the top of this page (left hand side) and insert 'life insurance' you will bring up previous posts on this topic. There is also a page on the cancer research website dedicated to potential insurance companies although I think that most of these are for travel insurance.
Perhaps you'd be good enough to let us know if you have any success?
