I am with Directline, and they also charge for a green card. Without one, you only have the bare minimum insurance cover abroad - i.e. third party.
There are two main benefits with a green card - firstly you get your fully comprehensive cover for your whole holiday. Secondly, the document itself is universally recognised throughout Europe, so if you get pulled over or have an accident the local police won't have any trouble understanding it.
Last year we paid