Hi
I work with Travel Insurance. You didnt mention what age you were? Try companies like Direct Line, Halifax if the condition is really bad call All Clear they will insure everyone at a premium. Be wary about the Post Office they dont cover pre existing conditions. Also you could try Insure and Go my friend uses them all the time and she has diabeties and her premium is small. If you smoke at all it will put your premium up. and possibly be the result of not getting cover but Hypertension on its own is not difficult to get insurance