If you take out breakdown cover, read the small print very, very, very carefully.
I was in central France with the boat last summer and the car suffered a breakdown - not total failure but it went into a 'limp-home' mode. It was towed away and I was given a hire car - so far so good. However, I was later advised (over a week later) that the part was on back order and wouldn't be available until at least September. I would therefore either have to go home with the car on a flat-bed lorry or take the hire car home and come back when the car was fixed! Then they hit me with the really bad news - the boat/trailer was too long to be covered under the breakdown recovery insurance. They could not / would not provide a hire car with a towbar, so the boat would have to remain in France until they could get around to fixing my car. Worse still, if I took the hire car home, I could not take it into the UK but would have to stop at a ferry port (I was booked on Eurotunnel), go across as a foot passenger (presumably with all my suitcases and heaps of boating gear...) and then collect another hire car at the UK ferry port. Furthermore, the car was only to be provided to get me home and would not be available whilst my car was off the road. Goodness knows what would become of the boat after it had been abandoned in France for a couple of months.
Fortunately, I managed to obtain the part number for the unobtainium part and sourced it from my local dealer at home. They posted it to the French dealer, who fitted it and got me mobile the day before I was due to leave - they had had the car from the day after I arrived on a two week holiday...
The moral of the story - be very careful about restrictions over the length, width, height and/or weight of your boat / trailer combination when you arrange insurance and ask what they will do about getting you home in the event of the breakdown of the towing vehicle.
Have a nice trip!