sdsearch - I agree with the point you made with regards to credit cards, Avis does let you only register 1, however I use Hertz for business and have multiple cards listed. Avis I only use for personal use - so not a problem for me.

In the UK we can't use our cards ( Visa etc ) for CDW its not offered to us.

Finally the savings offered by Avis BA compared to Avis.co.uk are only very slight - so have never used PC or collected points with the BA site