I have previously used travelinsurance4medical.co.uk and had reasonable prices, but having just requested another quote, they have given me a ridiculous price.
Insureandgo seems to be the same company as travelinsurance4medical.co.uk would not insure me.
Insurancewith.co.uk was hopeless. Up to the point where I said my trip was under 31 days i listed my condition (as I had declared) as prostate cancer. After that point it changed to something like "metastatic recurring cancer - which it isn't. I even started again and the same happened.
(I should point out that I am 59, was diagnosed early, had treatment just under 2 years ago, PSA less than 0.1, and no real complications)
Then I tried comparethemarket and got much better prices, 40% of the price of travelinsurance4medical.co.uk
The lowest cost was TravelTime, which is a DeFaqto two star but I paid a bit more and went for CoverWise which is DeFaqto 4 star.
Hope this is useful!