Lucifer,
Whilst it would be nice to be exempt from tax on this benefit in kind it is rather stretching the imagination to suggest it is wholly exclusively and necessary to undertake the job.
It is a discretionary insurance policy. It may be wise to have it but it is not necessary. Other insurance benefits such as PHI (permanant health insurance) may be considered as a complementary or alternative benefit so it it is not exclusive.
I suspect that drawing attention to other benefits such as free car parking and indeed staff travel perks will do little to enhance the arguement and no doubt the revenue are keenly looking at ways to bring these within their future remit.