When I started flying about two years ago I took out life insurance with one of the larger companies. I told them about the flying and had to fill in an aviation questionairre. The premiums turned out to be the same as without the aviation bit. In fact the premiums are less than those quoted by some of the specialists aviation life insurance companies you can find in the usual mags. At the end of the day if you don't tell them about your activities and any claim is refused, it would cost you, and more importantly your dependants, a lot more than a few quid a month.
PM me if you are interested in knowing the name of the company I decided to use.
D