In reply to JLS:
I purposely got one for Australia, as would have been a disaster turning up at the campervan hire place without, but was never asked for.
I don't think it's really worth the paper it's printed on, but, as said, for £7, it's worth the peace of mind.
You might as well tick every country on it, not just the one(s) you're intending getting it for.
More importantly, don't forget the DVLA codes for your actual driving licence - you will, for some reason, need your National Insurance number: https://www.gov.uk/view-driving-licence