I was in a similar position at the beginning of the year, my car is a 93 1700 SuperSprint, that had only cover 6868 miles, and almost non since 2003. I spent the winter going over all the essentials, and replacing hoses, belts and bushes. Since then I have been building up the miles for next weekend, were the plan is Donnington followed by a few days in Wales. I know its not as far, but its still way more miles and continuous hours than it's done for years, and I am confident because I have built up the miles and trust since spring. Given your car was rebuilt in 2016, I think you have less to worry about. Parts tend to either fail quickly, or give good service life, and it sounds like your car is in that window of "good service life" since the rebuild. Obviously the cars track record isn't great in France, but I would be confident if you can get a few miles done before you go. Also there are plenty of older cars running around France and the rest of Europe, so I am sure sourcing that obscure part won't be impossible if the worst should happen.