Thanks.
I did take a look there but it looks like the disc for the SL is a quite a specific one, [ this might be it part no. A2118273365] limited to around 3 models, but i am not sure about this or if its worth upgrading, i also took a look at the Mercedes shop, the one i thought was the correct one on their site was [ B67824069] this looked older the the one at Comand on line, so any help welcome.