From the UK life insurance perspective:
Flying, or indeed any activity whatsoever, is fully covered by a pre-existing life policy unless the activity is specifically excluded.
The trick might be getting insured after one has taken up flying.
IME, there is no problem if you fly 50-100hrs/year and if one shops around the companies, one finds one which doesn't care that much. There have also been some brokers advertising in the backs of the flying mags which sell some stuff like that.