I am in Les Landes in France and this evening at 6 O'clock (French time) I went for a walk and saw 7 small birds on a pine tree. They were about the size of a wren but used their tail to climb up the tree. They are not treecreepers as they do not spiral up the tree and they are too small. The light was bad but they had dark, probably brown, plumage and a pale breast like a tree creeper. They all came out of a small hole in the tree and only went up the tree, not spiraling. I am sorry I don't have a picture but hopefully you will be able to help me find a bird like this. Please suggest anything other than a tree creeper that climbs trees because i can't find anything. Thankyou.
Based on your description it must be a Treecreeper. I can't think of any other European bird that climbs tree trunks using its tail, is brown with a pale breast, and Wren size. In that area of SW France you should have the Short-toed treecreeper (Certhia brachydactyla). They don't have to spiral up the trees to be Treecreepers. They can go straight up; the real distinction you must make is they don't climb down like Nuthatches, they just go up, then fly to the base of another tree. They normally spiral to cover more of the tree bark when searching for food. At 6 PM they probably moved to a better tree crevice to go to sleep. Well, that's my best guess in the absence of a photo.