Depending on exactly what you want the options are vast, you mention good scenic roads, the best of these are unfortunately a little ride away.
The Black Forest is about 400 miles from Calais, the Vosges just a shade further, the Alps start about 500 miles from Calais, and the Pyrenees about 600.
Assuming your week involves to and from France I would suggest heading for the Black Forest and or the Vosges, as from your neck of the woods it is gonna use up about 1.5 days in each direction.
I would suggest starting very early on day one and getting a little way into France, my favoured spot is Two Wheel Moorings near Verdun.
From here you are only 3 hours from the Vosges / Black Forest, which means you could get there on day 2, drop off your bags and get some riding in.
This would leave 3 clear days for just riding around if you use one base, it is possible to get in and out of the Vosges and Black Forest from one Hotel and that gives great flexibility with weather, or you could use two Hotels each for two nights and still have the option of switching between the Black Forest and Vosges.
Both areas have a good few days riding in them so you could just do one in more depth, but even combined are a tiny fraction of the size of the Alps which is really a bit much to get into with so little time IMO.
I have no idea of your budgets, but if you want value Pension Williams is about as good as it gets (about £25 pppn if sharing) and is bang in the middle of the Black Forest with the Vosges just over an hour down the Autobahn, or about 1 1/2 - 2 hours if riding through the Black Forest.
The other oprion would be to keep moving with a different Hotel each night, but I personally find this quite irksome as you always seem to be packing / unpacking / checking in / checking out.
Check out tour reviews around here, I have one for the Black Forest:
http://www.ukgser.com/forums/showthread.php?t=249110
I think wapping loaded the ADAC Black Forest and Vosges routes somewhere on the site as well.