I has some luck with the Wesleyan, about 20 years ago, but my policy is far more expensive than a person with no diabetes, has a 13week deferment period and cover ends when I reach 55 years. It might be worth contacting the Wesleyan but it maybe that there is less willingness to cover people with D nowadays even on less favourable terms, due to increasing incidence/ prevalence ( or higher rates of diagnosis) plus more knowledge regarding actuarial risk.
Other option- get some expert financial advice regarding other financial products/ investments to put away for a rainy day and consider how if needed you could cut back on living expenses or other sources of income if unable to work such as whether possible to let out a room etc