Hi Nigel
We drove down from Dunkerque to Croatia via France, Luxembourg, Germany and Austria. We stopped off at:
Camping Buttelwoog - 1night
http://www.ukcampsite.co.uk/sites/reviews.asp?revid=10535
Camping Panorama Harras - 2 nights
http://www.ukcampsite.co.uk/sites/reviews.asp?revid=10437
and then entered Slovenia via the Karawanken Tunnel
On the way home we drove through Slovenia and into Austria near Linz
Service near Zagreb - 1 night!
Internationaler Campingplatz Nabtaal - 2 nights
http://www.ukcampsite.co.uk/sites/reviews.asp?revid=10536
We found it LONG journey - the car mileage from home in St Helens and back again was 3,303 miles!!
We used the autoroutes/motorways for our journey, free ones in France and Germany and paid for vignettes in Austrian and Slovenia - bought at service stations/border posts, and toll booths in Croatia. Check toll vignettes carefully. On our way home Cary misread the date on our Austrian vignette, it had expired, and we got stopped and fined €100 by a motorway official!!! There are some additional tunnel tolls in Austria.
All of the roads on our routes were good. The Croatian motorway was very new and very quiet. Croatian roads away from the motorway could be both congested, beware the coast road in Croatia for congestion, and sometimes scary when towing, eg, narrow with unguarded hairpins. Croatia was the least sophisticated country, not yet in the EU, so their own currency, but English was very widely spoken. Parking was very hard to find in Split.
Please post again if you have any further questions.
Went went in July/August so it would be much quieter in May when you plan to go.
Best wishes
Tim