We find there is more demand for twin rooms. We can put the beds together and some people do it anyway.
Also if you have one person in the room, you don't have so much linen to wash.
Agree singles give more flexiability but we would opt for a double where everything else was equal for a weeks holiday even now. All the websites I found were UK based but some of the makes/marques like Seally are available in France. If you want to buy in France suggest printout a few details then do a tour of the French bed shops with proof they exist.
http://www.beds2u.co.uk/shop.php?viewcategory=92&PHPSESSID=d01878c2bba66adf62dd949d18515ade
http://www.sleepingsolutions.co.uk/home.php?cat=6
http://www.bedstar.co.uk/shop/catalog/Bed_category_Zip__Link-p-1-c-263.html
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