In reply to tingle:
This is how I see it, and I do a lot of trips abroad. Thanks for the opportunity to list the possibilities - I'm just trying to decide which way to cover my own upcoming climbing trip to USA.
First you have the insurance which comes with AAC membership. This is limited to search and rescue (€25000) and immediate medical care thereafter plus repatriation (€10000)
If you're happy those figures (+ EHIC where appropriate) will get you off the hill, stabilised and back to UK from whatever country you find yourself in that's fine as far as "climbing insurance" goes, but you'll still need a normal travel insurance policy as well to cover the rest - illness, accident, cancellations, luggage, all the usual holiday abroad stuff. These are very cheap but obviously do not cover injuries sustained in hazardous pursuits, hence this discussion.
If you consider more cover in higher amounts is necessary for your chosen venue you have a number of options:
1) you can buy a top-up from the AAC - this gets you cover up to €500,000. Has to be done direct with their agent in Austria and the on-line form is in German but it goes OK - I've done it for Morocco trips. From memory it cost me around £60 for 2 weeks cover.
2) you can buy an additional policy from e.g. BMC or Snowcard. Many swear by them. Never been cheap for me as I already have annual travel insurance through my bank account and since BMC etc include all such cover as well as rescue etc it means I'm paying twice for the same thing. (Incidentally now I'm over 70 years old the "age loading" on these policies is prohibitive - BMC goes up by THREE times to around £400 for 18 days!!!) Snowcard yet more.
3) you can buy a hazardous activities "top-up" policy from for instance, the above mentioned Sportscover Direct. I've done this too and will probably be doing it this time since USA is reputed to have extortionate hospital bills and maybe the AAC extra to €500,000 is insufficient - Sportscover covers £10,000,000 and for my next trip is quoted at £135 for 16 days (and for me the age loading "only" doubles it). A benefit of this type of policy is that you only buy it for the days you might be exposed to risk, not travelling days at each end also.
I hope that helps a bit - it's helped me list all my options, so thanks again.