If you want to go abroad and find some interesting roads, the nearest great biking area is the Eifel region of Germany. A pleasant days trot, or four hours if you tuck in a bit, it's most famous attraction is the Nurburgring. But you don't need to ride the circuit to get your kicks, all the roads around the area are awesome for biking. It's not a densely populated area, although there are plenty of hotels, but it's best to book in advance cos many of them shut out of season.
Holland's full of very lovely people, but the roads are boring as buggery, and I've never found anything of interest in Belgium. France is cool, but the interesting roads are a long way south. Worth it once you get there, though, the Languedoc area is biking nirvana, and anywhere in the south will be warm and picturesque. Hotels just about everywhere, and little need to book. Or you can use the network of Formule 1 or Campanile hotels (among others), these are generally on the outskirts of large towns and are cheap (starting from 30 euros per room, so if there's 2 or 3 of you it's as cheap as camping).
There are some interesting roads in northern France, but they're well off the beaten track. Program your satnav to avoid motorways, stick it on landscape view, and head for anywhere where the road looks wiggly. I went on a 2500-mile, 7-day tour of France last year without touching a single motorway, and we had fun all the way. The south of France is do-able in a day, but it's a long old slog. It's a big country is France.
Switzerland is full of great roads, but you have to pay a 40 euro vignette to use their motorways, and they're a cheerless bunch of bastards. They'll take all your euros and give you the change back in swiss francs, the gits. Italy is Great, but I just can't get on with the people, just a personal preference you understand. And Spain has all the space and roads you crave, but again it's a long old slog to get there. Worth the effort if you've got the time.
You could tour round Britain, but you will get wet, and you will get stuck in traffic. So hit the chunnel and find out what touring by bike is all about; open, perfectly surfaced twisty roads, great scenery, great food, great people, great weather. The further south you go, the better all of the above gets. And you've got the perfect bike for the job. Have fun!