Except this little chap appears to be a small toad. In fact, I am pretty sure it is a midwife toad. A characteristic sound of summer nights in south western Europe is the high, bell like poo...... poo....... poo...... call of midwife toads, which often live in piles of stones and in the crevices of walls. Unlike nearly all other European frogs and toads, these secretive animals care for their eggs, which are laid in strings and carried by the male around his hind legs; he carries them until they are ready to hatch into tadpoles. These toads are quite small with a length of only 5 cms, a little more than 2 inches.
When planting out some seedlings, we found him/her under the little pots in the seed tray. As you can see he/she is covered in mud. You can clearly see the reddish line down his/her side on the third photograph.
We let it go into the sorrel, which is thick and bushy, and very damp underneath, so it could decide where it wanted to move to next.
Here is a better picture of the male carrying the eggs.
Picture credit http://www.ifrog.us/wp-content/gallery/discoglossidae-disc-tongued-frogs/midwife-toad.jpg