In reply to Steve_90:
You won't get charged for a rescue. In national and provincial parks there are rescue specialists (basically mountain guides) and contracted helicopter companies. Outside the parks there's volunteer SAR teams. I've been involved in initiating a couple of rescues via sat phone to the local RCMP, and no one has ever been charged either in parks, or outside them.
The issue will be the medical treatment, so you will need a policy that doesn't exclude climbing from the cover. My step mother has a mini-stroke and all up it was well over 20k GBP.