Taken my (Previous) 156 to Holland and France, without any problem, in fact it came from Holland. You shouldn't have a problem....look for the Sans Plomb..and watch out for the Gendarme, they have a thing about catching Brits speeding.
We hired a Roof Box, for a long drive down to the South of France a while back, it was one of those Streamlined 'Thule' Jobbies. The car at that time was a 405SRi, the Box took a bit off the top end speed, and blocked the Sun Roof, but apart from that was a very usefull thing to have.
Driving in France is far less hasle than the UK, enjoy yourself..
I've been commuting back and forth to France for the last 3 and a half years, it's great I love it.
I have had problems with my car abroad and guess what! you get seen nearly straight away! Even though the Alfa dealers are still *****.