Critical illness cover

It all depends on the details. There are several ways to proceed.
Firstly you should try to find a IFA or protection insurance specialist who is prepared to research your chances and likely terms offered by the major insurers. Unfortunately, they don't always offer this service, as it is very time consuming and not always going to result in a sale for them. However, there are brokers out there who will be prepared to do this.
If you don't get any joy from that route, you would do well to find a broker who specialises in cases that are difficult to place in the normal way. Some have an arrangement whereby you fill out one application form, which is submitted to several insurers at once. This saves a lot of time.
Finally, if you cant get any cover through these options you can take out a policy that excludes pre-existing conditions. Again, not easy to find using the 'traditional routes' but there are around.
Hope that helps.

My company has helped get CI cover in these circumstances before however the best you can hope for is an exclusion for Leukaemia and other cancers. In this circumstance you have to ask yourself if it is worth buying as around 50% of claims under CI cover are cancer related