Thanks... have done some checking and the 'spouse clause' applies to Avis Preferred in the US and Canada... the European rules state that 'the vehicle may not be operated by any person other than the Customer or any person nominated by the Customer who is approved by Avis at the time of rental'. So Alex is automatically covered on my Nevada hire, but not my France one...

Can't find a way of reaching the Hertz conditions without signing up, but might sign up anyway (since it's free...)