What the Automobile Association's AA Car Insurance has to offer is unclear, aside from the fact that the insurance is underwritten by the well-known Auto & General Insurance.
The Car insurance link on the AA website takes you to an online form. Online banner adverts (on other websites) take you to the same form. The form gives you no details of the insurance offered but does ask you for your AA membership number, but whether this means that participation is restricted to AA members is not indicated.