I had exactly this problem when I had to get life insurance back in 2009. I had to really shop around and eventually I found someone who would give me a reasonable quote provided I only went caving 20 times a year *cough cough *.
What's really stupid is none of the brokers cared about me commuting 100 miles a day on a motorbike in peak traffic times.
I'm going through a similar thing to you and the OP.
I commute by motorbike through central London, shortly to be even further - from Surrey to central London.
I'm also just buying my first house at the moment, and looking at various insurance products.
Aviva life insurance (decreasing cover for the life of the mortgage) has come out at under £20/month all in, to cover both of us.
I specifically asked, and my broker (also my mortgage broker) checked and confirmed that there was no exclusion or uplift for caving activities.
Taking this out for at least 6 months waives a huge chunk of his fee. No brainer.
I've also just been through the same conversation with the life cover & critical illness cover provided by my employer. Both of those are "on risk" 100% of the time, regardless of what I am doing, or where I am. Nice.
I am in the process of looking at arranging my own income protection, because if I injure myself and can't work, I currently have no plan.
I'm going through Summit FS, based on recommendations from this forum.
I've spoken to them a little, but not had a chance to get a full quote, as I've been abroad with work a fair amount recently.
Good luck with your search, and do try Summit FS. They seem to understand "us" even through their main market seems to be climbers and mountaineers.