I can honestly say I never look at the amount covered for cancellation because of accident or something, until I had to claim!
I have the free annual insurance from my premier account at lloyds, and cancellation cover is 5k, which nicely covers my trip in club. The insurance is underwritten by Axa, and they've been great to deal with.
Something I keenly look at is medical cover and repatriation when abroad as I tend to go off the beaten track!