Just thought I would add a postscript to this thread.
Our Vinci tag arrived less than 1 hour after we left for Le Mans

so we were unable to use it on that trip. We go to France reasonably often and we have just traversed southern France on our way back from Caramulo in Portugal.
The Vinci tag worked perfectly and we were able to breeze through the reserved lanes with perfect nonchalance, though I must admit wit used the non-reserved e-tag enabled lanes the first couple of times.
Our Morgan is equipped with sun-visors and I have made a Velcro strap in a matching colour to hold the Italian E-Tag to the top of the visor and that also worked fine, hood up or down, with the Vinci E-tag. I am sure it saved us a lot of time and frustration on the trip as we passed through 21 toll gates. I would say more than 1 hour of time save on the trip. We saw several cares hesitate to follow us in the reserved lanes and I could imagine what they were thinking
The tag that I have is the Télépéage Temps Libre
http://www.vinci-autoroutes.com/fr/temps-libre-telepeageOne small note to anyone ordering a Vinci tag. When you fill in the form giving your bank details you must attach a document from your bank which give your full bank details. What they ask for is a RIB (Relevé d'Identité Bancaire) - in France you get them at the back of your chequebook, and it's a cheque-sized slip containing the name and number of your account, branch, Swift no. etc. I asked my bank to print me those details and they gave me a copy stamped and dated with a bank rubber stamp to make it official
Thanks to Phillip for suggesting Vinci.